Datenschutz vollmacht fixed, two time counter added

backend/dist/controllers/contract.controller.d.ts

@@ -11,5 +11,7 @@ export declare function getSimCardCredentials(req: Request, res: Response): Prom
 export declare function getInternetCredentials(req: Request, res: Response): Promise<void>;
 export declare function getSipCredentials(req: Request, res: Response): Promise<void>;
 export declare function getCockpit(req: AuthRequest, res: Response): Promise<void>;
+export declare function addSuccessorMeter(req: AuthRequest, res: Response): Promise<void>;
+export declare function removeContractMeter(req: AuthRequest, res: Response): Promise<void>;
 export declare function snoozeContract(req: Request, res: Response): Promise<void>;
 //# sourceMappingURL=contract.controller.d.ts.map

backend/dist/controllers/contract.controller.d.ts.map

@@ -1 +1 @@
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backend/dist/controllers/contract.controller.js

@@ -44,6 +44,8 @@ exports.getSimCardCredentials = getSimCardCredentials;
 exports.getInternetCredentials = getInternetCredentials;
 exports.getSipCredentials = getSipCredentials;
 exports.getCockpit = getCockpit;
+exports.addSuccessorMeter = addSuccessorMeter;
+exports.removeContractMeter = removeContractMeter;
 exports.snoozeContract = snoozeContract;
 const client_1 = require("@prisma/client");
 const contractService = __importStar(require("../services/contract.service.js"));
@@ -265,6 +267,71 @@ async function getCockpit(req, res) {
         });
     }
 }
+// ==================== FOLGEZÄHLER ====================
+async function addSuccessorMeter(req, res) {
+    try {
+        const contractId = parseInt(req.params.id);
+        const { meterId, installedAt, finalReadingPrevious } = req.body;
+        const contract = await prisma.contract.findUnique({
+            where: { id: contractId },
+            include: { energyDetails: { include: { contractMeters: { orderBy: { position: 'asc' } } } } },
+        });
+        if (!contract?.energyDetails) {
+            res.status(404).json({ success: false, error: 'Energievertrag nicht gefunden' });
+            return;
+        }
+        const ecdId = contract.energyDetails.id;
+        const existingMeters = contract.energyDetails.contractMeters;
+        const nextPosition = existingMeters.length > 0
+            ? Math.max(...existingMeters.map(m => m.position)) + 1
+            : 0;
+        // Vorherigen Zähler als gewechselt markieren
+        if (existingMeters.length > 0 && finalReadingPrevious !== undefined) {
+            const prevMeter = existingMeters[existingMeters.length - 1];
+            await prisma.contractMeter.update({
+                where: { id: prevMeter.id },
+                data: {
+                    removedAt: installedAt ? new Date(installedAt) : new Date(),
+                    finalReading: parseFloat(finalReadingPrevious),
+                },
+            });
+        }
+        const contractMeter = await prisma.contractMeter.create({
+            data: {
+                energyContractDetailsId: ecdId,
+                meterId: parseInt(meterId),
+                position: nextPosition,
+                installedAt: installedAt ? new Date(installedAt) : new Date(),
+            },
+            include: { meter: { include: { readings: true } } },
+        });
+        // Aktuellen Zähler am Vertrag aktualisieren
+        await prisma.energyContractDetails.update({
+            where: { id: ecdId },
+            data: { meterId: parseInt(meterId) },
+        });
+        res.json({ success: true, data: contractMeter });
+    }
+    catch (error) {
+        res.status(400).json({
+            success: false,
+            error: error instanceof Error ? error.message : 'Fehler beim Hinzufügen des Folgezählers',
+        });
+    }
+}
+async function removeContractMeter(req, res) {
+    try {
+        const contractMeterId = parseInt(req.params.contractMeterId);
+        await prisma.contractMeter.delete({ where: { id: contractMeterId } });
+        res.json({ success: true, data: null });
+    }
+    catch (error) {
+        res.status(400).json({
+            success: false,
+            error: error instanceof Error ? error.message : 'Fehler beim Entfernen',
+        });
+    }
+}
 // ==================== SNOOZE (VERTRAG ZURÜCKSTELLEN) ====================
 async function snoozeContract(req, res) {
     try {

backend/dist/controllers/customer.controller.d.ts.map

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backend/dist/controllers/customer.controller.js

@@ -351,7 +351,14 @@ async function getMeterReadings(req, res) {
 }
 async function addMeterReading(req, res) {
     try {
-        const reading = await customerService.addMeterReading(parseInt(req.params.meterId), req.body);
+        const { readingDate, value, valueNt, unit, notes } = req.body;
+        const reading = await customerService.addMeterReading(parseInt(req.params.meterId), {
+            readingDate: new Date(readingDate),
+            value: parseFloat(value),
+            valueNt: valueNt !== undefined && valueNt !== null && valueNt !== '' ? parseFloat(valueNt) : undefined,
+            unit,
+            notes,
+        });
         res.status(201).json({ success: true, data: reading });
     }
     catch (error) {
@@ -363,7 +370,19 @@ async function addMeterReading(req, res) {
 }
 async function updateMeterReading(req, res) {
     try {
-        const reading = await customerService.updateMeterReading(parseInt(req.params.meterId), parseInt(req.params.readingId), req.body);
+        const { readingDate, value, valueNt, unit, notes } = req.body;
+        const updateData = {};
+        if (readingDate !== undefined)
+            updateData.readingDate = new Date(readingDate);
+        if (value !== undefined)
+            updateData.value = parseFloat(value);
+        if (valueNt !== undefined)
+            updateData.valueNt = valueNt !== null && valueNt !== '' ? parseFloat(valueNt) : null;
+        if (unit !== undefined)
+            updateData.unit = unit;
+        if (notes !== undefined)
+            updateData.notes = notes;
+        const reading = await customerService.updateMeterReading(parseInt(req.params.meterId), parseInt(req.params.readingId), updateData);
         res.json({ success: true, data: reading });
     }
     catch (error) {
@@ -404,15 +423,18 @@ async function reportMeterReading(req, res) {
             res.status(403).json({ success: false, error: 'Kein Zugriff auf diesen Zähler' });
             return;
         }
-        const reading = await prisma.meterReading.create({
+        const parsedDate = readingDate ? new Date(readingDate) : new Date();
-            data: {
+        const parsedValue = parseFloat(value);
-                meterId,
+        // Validierung über den Service (monoton steigend)
-                value: parseFloat(value),
+        const reading = await customerService.addMeterReading(meterId, {
-                readingDate: readingDate ? new Date(readingDate) : new Date(),
+            readingDate: parsedDate,
-                notes,
+            value: parsedValue,
-                reportedBy: user.email,
+            notes,
-                status: 'REPORTED',
+        });
-            },
+        // Status auf REPORTED setzen
+        await prisma.meterReading.update({
+            where: { id: reading.id },
+            data: { reportedBy: user.email, status: 'REPORTED' },
         });
         res.status(201).json({ success: true, data: reading });
     }

backend/dist/routes/contract.routes.d.ts.map

@@ -1 +1 @@
-{"version":3,"file":"contract.routes.d.ts","sourceRoot":"","sources":["../../src/routes/contract.routes.ts"],"names":[],"mappings":"AAIA,QAAA,MAAM,MAAM,4CAAW,CAAC;AA8BxB,eAAe,MAAM,CAAC"}
+{"version":3,"file":"contract.routes.d.ts","sourceRoot":"","sources":["../../src/routes/contract.routes.ts"],"names":[],"mappings":"AAIA,QAAA,MAAM,MAAM,4CAAW,CAAC;AAkCxB,eAAe,MAAM,CAAC"}

backend/dist/routes/contract.routes.js

@@ -48,6 +48,9 @@ router.delete('/:id', auth_js_1.authenticate, (0, auth_js_1.requirePermission)('
 router.post('/:id/follow-up', auth_js_1.authenticate, (0, auth_js_1.requirePermission)('contracts:create'), contractController.createFollowUp);
 // Snooze (Vertrag zurückstellen)
 router.patch('/:id/snooze', auth_js_1.authenticate, (0, auth_js_1.requirePermission)('contracts:update'), contractController.snoozeContract);
+// Folgezähler
+router.post('/:id/successor-meter', auth_js_1.authenticate, (0, auth_js_1.requirePermission)('contracts:update'), contractController.addSuccessorMeter);
+router.delete('/:id/contract-meter/:contractMeterId', auth_js_1.authenticate, (0, auth_js_1.requirePermission)('contracts:update'), contractController.removeContractMeter);
 // Get decrypted password
 router.get('/:id/password', auth_js_1.authenticate, (0, auth_js_1.requirePermission)('contracts:read'), contractController.getContractPassword);
 // Get decrypted SimCard PIN/PUK

backend/dist/routes/contract.routes.js.map

@@ -1 +1 @@
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+{"version":3,"file":"contract.routes.js","sourceRoot":"","sources":["../../src/routes/contract.routes.ts"],"names":[],"mappings":";;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;AAAA,qCAAiC;AACjC,0FAA4E;AAC5E,mDAAwE;AAExE,MAAM,MAAM,GAAG,IAAA,gBAAM,GAAE,CAAC;AAExB,MAAM,CAAC,GAAG,CAAC,GAAG,EAAE,sBAAY,EAAE,IAAA,2BAAiB,EAAC,gBAAgB,CAAC,EAAE,kBAAkB,CAAC,YAAY,CAAC,CAAC;AACpG,MAAM,CAAC,IAAI,CAAC,GAAG,EAAE,sBAAY,EAAE,IAAA,2BAAiB,EAAC,kBAAkB,CAAC,EAAE,kBAAkB,CAAC,cAAc,CAAC,CAAC;AAEzG,2CAA2C;AAC3C,MAAM,CAAC,GAAG,CAAC,UAAU,EAAE,sBAAY,EAAE,IAAA,2BAAiB,EAAC,gBAAgB,CAAC,EAAE,kBAAkB,CAAC,UAAU,CAAC,CAAC;AAEzG,MAAM,CAAC,GAAG,CAAC,MAAM,EAAE,sBAAY,EAAE,IAAA,2BAAiB,EAAC,gBAAgB,CAAC,EAAE,kBAAkB,CAAC,WAAW,CAAC,CAAC;AACtG,MAAM,CAAC,GAAG,CAAC,MAAM,EAAE,sBAAY,EAAE,IAAA,2BAAiB,EAAC,kBAAkB,CAAC,EAAE,kBAAkB,CAAC,cAAc,CAAC,CAAC;AAC3G,MAAM,CAAC,MAAM,CAAC,MAAM,EAAE,sBAAY,EAAE,IAAA,2BAAiB,EAAC,kBAAkB,CAAC,EAAE,kBAAkB,CAAC,cAAc,CAAC,CAAC;AAE9G,qBAAqB;AACrB,MAAM,CAAC,IAAI,CAAC,gBAAgB,EAAE,sBAAY,EAAE,IAAA,2BAAiB,EAAC,kBAAkB,CAAC,EAAE,kBAAkB,CAAC,cAAc,CAAC,CAAC;AAEtH,iCAAiC;AACjC,MAAM,CAAC,KAAK,CAAC,aAAa,EAAE,sBAAY,EAAE,IAAA,2BAAiB,EAAC,kBAAkB,CAAC,EAAE,kBAAkB,CAAC,cAAc,CAAC,CAAC;AAEpH,cAAc;AACd,MAAM,CAAC,IAAI,CAAC,sBAAsB,EAAE,sBAAY,EAAE,IAAA,2BAAiB,EAAC,kBAAkB,CAAC,EAAE,kBAAkB,CAAC,iBAAiB,CAAC,CAAC;AAC/H,MAAM,CAAC,MAAM,CAAC,sCAAsC,EAAE,sBAAY,EAAE,IAAA,2BAAiB,EAAC,kBAAkB,CAAC,EAAE,kBAAkB,CAAC,mBAAmB,CAAC,CAAC;AAEnJ,yBAAyB;AACzB,MAAM,CAAC,GAAG,CAAC,eAAe,EAAE,sBAAY,EAAE,IAAA,2BAAiB,EAAC,gBAAgB,CAAC,EAAE,kBAAkB,CAAC,mBAAmB,CAAC,CAAC;AAEvH,gCAAgC;AAChC,MAAM,CAAC,GAAG,CAAC,iCAAiC,EAAE,sBAAY,EAAE,IAAA,2BAAiB,EAAC,gBAAgB,CAAC,EAAE,kBAAkB,CAAC,qBAAqB,CAAC,CAAC;AAE3I,kCAAkC;AAClC,MAAM,CAAC,GAAG,CAAC,2BAA2B,EAAE,sBAAY,EAAE,IAAA,2BAAiB,EAAC,gBAAgB,CAAC,EAAE,kBAAkB,CAAC,sBAAsB,CAAC,CAAC;AAEtI,6BAA6B;AAC7B,MAAM,CAAC,GAAG,CAAC,6CAA6C,EAAE,sBAAY,EAAE,IAAA,2BAAiB,EAAC,gBAAgB,CAAC,EAAE,kBAAkB,CAAC,iBAAiB,CAAC,CAAC;AAEnJ,kBAAe,MAAM,CAAC"}

backend/dist/routes/upload.routes.d.ts.map

@@ -1 +1 @@
-{"version":3,"file":"upload.routes.d.ts","sourceRoot":"","sources":["../../src/routes/upload.routes.ts"],"names":[],"mappings":"AAQA,QAAA,MAAM,MAAM,4CAAW,CAAC;AA2uBxB,eAAe,MAAM,CAAC"}
+{"version":3,"file":"upload.routes.d.ts","sourceRoot":"","sources":["../../src/routes/upload.routes.ts"],"names":[],"mappings":"AAQA,QAAA,MAAM,MAAM,4CAAW,CAAC;AA2vBxB,eAAe,MAAM,CAAC"}

backend/dist/routes/upload.routes.js

@@ -338,6 +338,15 @@ router.post('/customers/:id/privacy-policy', auth_js_1.authenticate, (0, auth_js
             where: { id: customerId },
             data: { privacyPolicyPath: relativePath },
         });
+        // Alle Consents auf GRANTED setzen (PDF = vollständige Einwilligung)
+        const consentTypes = ['DATA_PROCESSING', 'MARKETING_EMAIL', 'MARKETING_PHONE', 'DATA_SHARING_PARTNER'];
+        for (const consentType of consentTypes) {
+            await prisma.customerConsent.upsert({
+                where: { customerId_consentType: { customerId, consentType } },
+                update: { status: 'GRANTED', grantedAt: new Date(), source: 'papier' },
+                create: { customerId, consentType, status: 'GRANTED', grantedAt: new Date(), source: 'papier', createdBy: req.user?.email || 'admin' },
+            });
+        }
         res.json({
             success: true,
             data: {
@@ -376,6 +385,11 @@ router.delete('/customers/:id/privacy-policy', auth_js_1.authenticate, (0, auth_
             where: { id: customerId },
             data: { privacyPolicyPath: null },
         });
+        // Nur Consents widerrufen die per Papier erteilt wurden
+        await prisma.customerConsent.updateMany({
+            where: { customerId, status: 'GRANTED', source: 'papier' },
+            data: { status: 'WITHDRAWN', withdrawnAt: new Date() },
+        });
         res.json({ success: true });
     }
     catch (error) {

backend/dist/services/contract.service.js

@@ -122,14 +122,14 @@ async function getContractById(id, decryptPassword = false) {
             previousProvider: true,
             previousContract: {
                 include: {
-                    energyDetails: { include: { meter: { include: { readings: true } }, invoices: true } },
+                    energyDetails: { include: { meter: { include: { readings: true } }, contractMeters: { include: { meter: { include: { readings: true } } }, orderBy: { position: 'asc' } }, invoices: true } },
                     internetDetails: { include: { phoneNumbers: true } },
                     mobileDetails: { include: { simCards: true } },
                     tvDetails: true,
                     carInsuranceDetails: true,
                 },
             },
-            energyDetails: { include: { meter: { include: { readings: true } }, invoices: true } },
+            energyDetails: { include: { meter: { include: { readings: true } }, contractMeters: { include: { meter: { include: { readings: true } } }, orderBy: { position: 'asc' } }, invoices: true } },
             internetDetails: { include: { phoneNumbers: true } },
             mobileDetails: { include: { simCards: true } },
             tvDetails: true,
@@ -264,11 +264,41 @@ async function updateContract(id, data) {
     });
     // Update type-specific details
     if (energyDetails) {
+        const existingEcd = await prisma.energyContractDetails.findUnique({
+            where: { contractId: id },
+            select: { id: true, meterId: true },
+        });
         await prisma.energyContractDetails.upsert({
             where: { contractId: id },
             update: energyDetails,
             create: { contractId: id, ...energyDetails },
         });
+        // ContractMeter synchronisieren wenn sich der Zähler ändert
+        if (energyDetails.meterId !== undefined && existingEcd) {
+            const oldMeterId = existingEcd.meterId;
+            const newMeterId = energyDetails.meterId;
+            if (oldMeterId !== newMeterId) {
+                // Alle alten ContractMeter-Einträge entfernen
+                await prisma.contractMeter.deleteMany({
+                    where: { energyContractDetailsId: existingEcd.id },
+                });
+                // Neuen ContractMeter-Eintrag erstellen (wenn ein Zähler gesetzt)
+                if (newMeterId) {
+                    const contract = await prisma.contract.findUnique({
+                        where: { id },
+                        select: { startDate: true },
+                    });
+                    await prisma.contractMeter.create({
+                        data: {
+                            energyContractDetailsId: existingEcd.id,
+                            meterId: newMeterId,
+                            position: 0,
+                            installedAt: contract?.startDate,
+                        },
+                    });
+                }
+            }
+        }
     }
     if (internetDetails) {
         const { phoneNumbers, internetPassword, ...internetData } = internetDetails;

backend/dist/services/contractCockpit.service.d.ts

@@ -78,6 +78,10 @@ export interface ReportedMeterReading {
         customerNumber: string;
         name: string;
     };
+    contract?: {
+        id: number;
+        contractNumber: string;
+    };
     providerPortal?: {
         providerName: string;
         portalUrl: string;

backend/dist/services/contractCockpit.service.d.ts.map

@@ -1 +1 @@
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backend/dist/services/contractCockpit.service.js

@@ -682,6 +682,7 @@ async function getReportedMeterReadings() {
                             contract: {
                                 select: {
                                     id: true,
+                                    contractNumber: true,
                                     portalUsername: true,
                                     provider: {
                                         select: { id: true, name: true, portalUrl: true },
@@ -717,6 +718,10 @@ async function getReportedMeterReadings() {
                 customerNumber: r.meter.customer.customerNumber,
                 name: `${r.meter.customer.firstName} ${r.meter.customer.lastName}`,
             },
+            contract: contract ? {
+                id: contract.id,
+                contractNumber: contract.contractNumber,
+            } : undefined,
             providerPortal: provider?.portalUrl ? {
                 providerName: provider.name,
                 portalUrl: provider.portalUrl,

backend/dist/services/contractTask.service.d.ts

@@ -206,17 +206,17 @@ export declare function getAllTasks(filters: AllTasksFilters): Promise<({
             customerNumber: string;
             companyName: string | null;
         };
-        tariff: {
+        contractNumber: string;
-            id: number;
+        providerName: string | null;
-            name: string;
+        tariffName: string | null;
-        } | null;
         provider: {
             id: number;
             name: string;
         } | null;
-        tariffName: string | null;
+        tariff: {
-        providerName: string | null;
+            id: number;
-        contractNumber: string;
+            name: string;
+        } | null;
     };
     subtasks: {
         id: number;

backend/dist/services/customer.service.d.ts

@@ -107,13 +107,14 @@ export declare function getCustomerById(id: number): Promise<({
             createdAt: Date;
             notes: string | null;
             readingDate: Date;
+            meterId: number;
+            status: import(".prisma/client").$Enums.MeterReadingStatus;
             value: number;
+            valueNt: number | null;
             unit: string;
             reportedBy: string | null;
-            status: import(".prisma/client").$Enums.MeterReadingStatus;
             transferredAt: Date | null;
             transferredBy: string | null;
-            meterId: number;
         }[];
     } & {
         id: number;
@@ -123,6 +124,7 @@ export declare function getCustomerById(id: number): Promise<({
         updatedAt: Date;
         type: import(".prisma/client").$Enums.MeterType;
         meterNumber: string;
+        tariffModel: import(".prisma/client").$Enums.MeterTariffModel;
         location: string | null;
     })[];
     stressfreiEmails: {
@@ -171,11 +173,8 @@ export declare function getCustomerById(id: number): Promise<({
         notes: string | null;
         portalPasswordEncrypted: string | null;
         startDate: Date | null;
-        status: import(".prisma/client").$Enums.ContractStatus;
-        customerNumberAtProvider: string | null;
-        tariffName: string | null;
-        providerName: string | null;
         contractNumber: string;
+        status: import(".prisma/client").$Enums.ContractStatus;
         contractCategoryId: number | null;
         addressId: number | null;
         billingAddressId: number | null;
@@ -190,6 +189,9 @@ export declare function getCustomerById(id: number): Promise<({
         previousContractNumber: string | null;
         providerId: number | null;
         tariffId: number | null;
+        providerName: string | null;
+        tariffName: string | null;
+        customerNumberAtProvider: string | null;
         contractNumberAtProvider: string | null;
         priceFirst12Months: string | null;
         priceFrom13Months: string | null;
@@ -573,13 +575,14 @@ export declare function getCustomerMeters(customerId: number, showInactive?: boo
         createdAt: Date;
         notes: string | null;
         readingDate: Date;
+        meterId: number;
+        status: import(".prisma/client").$Enums.MeterReadingStatus;
         value: number;
+        valueNt: number | null;
         unit: string;
         reportedBy: string | null;
-        status: import(".prisma/client").$Enums.MeterReadingStatus;
         transferredAt: Date | null;
         transferredBy: string | null;
-        meterId: number;
     }[];
 } & {
     id: number;
@@ -589,6 +592,7 @@ export declare function getCustomerMeters(customerId: number, showInactive?: boo
     updatedAt: Date;
     type: import(".prisma/client").$Enums.MeterType;
     meterNumber: string;
+    tariffModel: import(".prisma/client").$Enums.MeterTariffModel;
     location: string | null;
 })[]>;
 export declare function createMeter(customerId: number, data: {
@@ -603,6 +607,7 @@ export declare function createMeter(customerId: number, data: {
     updatedAt: Date;
     type: import(".prisma/client").$Enums.MeterType;
     meterNumber: string;
+    tariffModel: import(".prisma/client").$Enums.MeterTariffModel;
     location: string | null;
 }>;
 export declare function updateMeter(id: number, data: {
@@ -618,6 +623,7 @@ export declare function updateMeter(id: number, data: {
     updatedAt: Date;
     type: import(".prisma/client").$Enums.MeterType;
     meterNumber: string;
+    tariffModel: import(".prisma/client").$Enums.MeterTariffModel;
     location: string | null;
 }>;
 export declare function deleteMeter(id: number): Promise<{
@@ -628,11 +634,13 @@ export declare function deleteMeter(id: number): Promise<{
     updatedAt: Date;
     type: import(".prisma/client").$Enums.MeterType;
     meterNumber: string;
+    tariffModel: import(".prisma/client").$Enums.MeterTariffModel;
     location: string | null;
 }>;
 export declare function addMeterReading(meterId: number, data: {
     readingDate: Date;
     value: number;
+    valueNt?: number;
     unit?: string;
     notes?: string;
 }): Promise<{
@@ -640,30 +648,33 @@ export declare function addMeterReading(meterId: number, data: {
     createdAt: Date;
     notes: string | null;
     readingDate: Date;
+    meterId: number;
+    status: import(".prisma/client").$Enums.MeterReadingStatus;
     value: number;
+    valueNt: number | null;
     unit: string;
     reportedBy: string | null;
-    status: import(".prisma/client").$Enums.MeterReadingStatus;
     transferredAt: Date | null;
     transferredBy: string | null;
-    meterId: number;
 }>;
 export declare function getMeterReadings(meterId: number): Promise<{
     id: number;
     createdAt: Date;
     notes: string | null;
     readingDate: Date;
+    meterId: number;
+    status: import(".prisma/client").$Enums.MeterReadingStatus;
     value: number;
+    valueNt: number | null;
     unit: string;
     reportedBy: string | null;
-    status: import(".prisma/client").$Enums.MeterReadingStatus;
     transferredAt: Date | null;
     transferredBy: string | null;
-    meterId: number;
 }[]>;
 export declare function updateMeterReading(meterId: number, readingId: number, data: {
     readingDate?: Date;
     value?: number;
+    valueNt?: number | null;
     unit?: string;
     notes?: string;
 }): Promise<{
@@ -671,26 +682,28 @@ export declare function updateMeterReading(meterId: number, readingId: number, d
     createdAt: Date;
     notes: string | null;
     readingDate: Date;
+    meterId: number;
+    status: import(".prisma/client").$Enums.MeterReadingStatus;
     value: number;
+    valueNt: number | null;
     unit: string;
     reportedBy: string | null;
-    status: import(".prisma/client").$Enums.MeterReadingStatus;
     transferredAt: Date | null;
     transferredBy: string | null;
-    meterId: number;
 }>;
 export declare function deleteMeterReading(meterId: number, readingId: number): Promise<{
     id: number;
     createdAt: Date;
     notes: string | null;
     readingDate: Date;
+    meterId: number;
+    status: import(".prisma/client").$Enums.MeterReadingStatus;
     value: number;
+    valueNt: number | null;
     unit: string;
     reportedBy: string | null;
-    status: import(".prisma/client").$Enums.MeterReadingStatus;
     transferredAt: Date | null;
     transferredBy: string | null;
-    meterId: number;
 }>;
 export declare function updatePortalSettings(customerId: number, data: {
     portalEnabled?: boolean;

backend/dist/services/customer.service.js

@@ -321,13 +321,42 @@ async function updateMeter(id, data) {
     });
 }
 async function deleteMeter(id) {
+    // Prüfen ob der Zähler noch an Verträgen hängt
+    const linkedContracts = await prisma.contractMeter.findMany({
+        where: { meterId: id },
+        include: { energyContractDetails: { include: { contract: { select: { contractNumber: true } } } } },
+    });
+    if (linkedContracts.length > 0) {
+        const contractNumbers = linkedContracts
+            .map(cm => cm.energyContractDetails.contract.contractNumber)
+            .join(', ');
+        throw new Error(`Zähler kann nicht gelöscht werden – noch an Vertrag/Verträgen zugeordnet: ${contractNumbers}`);
+    }
+    // Auch direkte meterId-Referenz auf EnergyContractDetails prüfen
+    const directLinks = await prisma.energyContractDetails.findMany({
+        where: { meterId: id },
+        include: { contract: { select: { contractNumber: true } } },
+    });
+    if (directLinks.length > 0) {
+        const contractNumbers = directLinks.map(d => d.contract.contractNumber).join(', ');
+        throw new Error(`Zähler kann nicht gelöscht werden – noch an Vertrag/Verträgen zugeordnet: ${contractNumbers}`);
+    }
     return prisma.meter.delete({ where: { id } });
 }
 async function addMeterReading(meterId, data) {
+    // Validierung: Zählerstand muss monoton steigend sein
+    await validateReadingValue(meterId, data.readingDate, data.value, undefined, 'HT');
+    if (data.valueNt !== undefined) {
+        await validateReadingValue(meterId, data.readingDate, data.valueNt, undefined, 'NT');
+    }
     return prisma.meterReading.create({
         data: {
             meterId,
-            ...data,
+            readingDate: data.readingDate,
+            value: data.value,
+            valueNt: data.valueNt,
+            unit: data.unit,
+            notes: data.notes,
         },
     });
 }
@@ -345,11 +374,46 @@ async function updateMeterReading(meterId, readingId, data) {
     if (!reading) {
         throw new Error('Zählerstand nicht gefunden');
     }
+    // Validierung bei Wertänderung
+    if (data.value !== undefined || data.readingDate !== undefined) {
+        await validateReadingValue(meterId, data.readingDate || reading.readingDate, data.value ?? reading.value, readingId, 'HT');
+    }
+    if (data.valueNt !== undefined || data.readingDate !== undefined) {
+        const ntVal = data.valueNt ?? reading.valueNt;
+        if (ntVal !== undefined && ntVal !== null) {
+            await validateReadingValue(meterId, data.readingDate || reading.readingDate, ntVal, readingId, 'NT');
+        }
+    }
     return prisma.meterReading.update({
         where: { id: readingId },
         data,
     });
 }
+/**
+ * Validiert, dass ein Zählerstand monoton steigend ist.
+ * tariffLabel: 'HT' für Hochtarif/Eintarif, 'NT' für Niedertarif
+ */
+async function validateReadingValue(meterId, readingDate, value, excludeReadingId, tariffLabel = 'HT') {
+    const existing = await prisma.meterReading.findMany({
+        where: { meterId, ...(excludeReadingId ? { id: { not: excludeReadingId } } : {}) },
+        orderBy: { readingDate: 'asc' },
+    });
+    const fmtDate = (d) => d.toLocaleDateString('de-DE', { day: '2-digit', month: '2-digit', year: 'numeric' });
+    const fmtVal = (v) => v.toLocaleString('de-DE');
+    const label = tariffLabel === 'NT' ? 'NT-Zählerstand' : 'Zählerstand';
+    // Vergleichswert aus bestehendem Reading extrahieren
+    const getVal = (r) => tariffLabel === 'NT' ? (r.valueNt ?? 0) : r.value;
+    // Stand vor dem neuen Datum
+    const before = [...existing].filter(r => r.readingDate <= readingDate).pop();
+    if (before && value < getVal(before)) {
+        throw new Error(`${label} (${fmtVal(value)}) darf nicht kleiner sein als der Stand vom ${fmtDate(before.readingDate)} (${fmtVal(getVal(before))})`);
+    }
+    // Stand nach dem neuen Datum
+    const after = existing.find(r => r.readingDate > readingDate);
+    if (after && value > getVal(after)) {
+        throw new Error(`${label} (${fmtVal(value)}) darf nicht größer sein als der spätere Stand vom ${fmtDate(after.readingDate)} (${fmtVal(getVal(after))})`);
+    }
+}
 async function deleteMeterReading(meterId, readingId) {
     // Verify the reading belongs to the meter
     const reading = await prisma.meterReading.findFirst({

backend/node_modules/.prisma/client/index-browser.js

@@ -361,6 +361,7 @@ exports.Prisma.MeterScalarFieldEnum = {
   customerId: 'customerId',
   meterNumber: 'meterNumber',
   type: 'type',
+  tariffModel: 'tariffModel',
   location: 'location',
   isActive: 'isActive',
   createdAt: 'createdAt',
@@ -372,6 +373,7 @@ exports.Prisma.MeterReadingScalarFieldEnum = {
   meterId: 'meterId',
   readingDate: 'readingDate',
   value: 'value',
+  valueNt: 'valueNt',
   unit: 'unit',
   notes: 'notes',
   reportedBy: 'reportedBy',
@@ -529,11 +531,23 @@ exports.Prisma.EnergyContractDetailsScalarFieldEnum = {
   annualConsumptionKwh: 'annualConsumptionKwh',
   basePrice: 'basePrice',
   unitPrice: 'unitPrice',
+  unitPriceNt: 'unitPriceNt',
   bonus: 'bonus',
   previousProviderName: 'previousProviderName',
   previousCustomerNumber: 'previousCustomerNumber'
 };
 
+exports.Prisma.ContractMeterScalarFieldEnum = {
+  id: 'id',
+  energyContractDetailsId: 'energyContractDetailsId',
+  meterId: 'meterId',
+  position: 'position',
+  installedAt: 'installedAt',
+  removedAt: 'removedAt',
+  finalReading: 'finalReading',
+  createdAt: 'createdAt'
+};
+
 exports.Prisma.InvoiceScalarFieldEnum = {
   id: 'id',
   energyContractDetailsId: 'energyContractDetailsId',
@@ -742,6 +756,11 @@ exports.MeterType = exports.$Enums.MeterType = {
   GAS: 'GAS'
 };
 
+exports.MeterTariffModel = exports.$Enums.MeterTariffModel = {
+  SINGLE: 'SINGLE',
+  DUAL: 'DUAL'
+};
+
 exports.MeterReadingStatus = exports.$Enums.MeterReadingStatus = {
   RECORDED: 'RECORDED',
   REPORTED: 'REPORTED',
@@ -855,6 +874,7 @@ exports.Prisma.ModelName = {
   ContractTask: 'ContractTask',
   ContractTaskSubtask: 'ContractTaskSubtask',
   EnergyContractDetails: 'EnergyContractDetails',
+  ContractMeter: 'ContractMeter',
   Invoice: 'Invoice',
   InternetContractDetails: 'InternetContractDetails',
   PhoneNumber: 'PhoneNumber',

backend/node_modules/.prisma/client/package.json

@@ -1,5 +1,5 @@
 {
-  "name": "prisma-client-c6d54e22fa4d6137f643638da5d523e99ce84f9544cc793fd89163f1612953c6",
+  "name": "prisma-client-45a91d7556f300a75a0048d27fac6a72915779fc4e5c2234b54fe3547ddb1605",
   "main": "index.js",
   "types": "index.d.ts",
   "browser": "index-browser.js",

backend/node_modules/.prisma/client/schema.prisma

@@ -411,18 +411,25 @@ enum MeterType {
   GAS
 }
 
+enum MeterTariffModel {
+  SINGLE // Eintarifzähler (Standard)
+  DUAL // Zweitarifzähler (HT/NT)
+}
+
 model Meter {
-  id            Int                     @id @default(autoincrement())
+  id             Int                     @id @default(autoincrement())
-  customerId    Int
+  customerId     Int
-  customer      Customer                @relation(fields: [customerId], references: [id], onDelete: Cascade)
+  customer       Customer                @relation(fields: [customerId], references: [id], onDelete: Cascade)
-  meterNumber   String
+  meterNumber    String
-  type          MeterType
+  type           MeterType
-  location      String?
+  tariffModel    MeterTariffModel        @default(SINGLE) // Eintarif oder Zweitarif (HT/NT)
-  isActive      Boolean                 @default(true)
+  location       String?
-  readings      MeterReading[]
+  isActive       Boolean                 @default(true)
-  energyDetails EnergyContractDetails[]
+  readings       MeterReading[]
-  createdAt     DateTime                @default(now())
+  energyDetails  EnergyContractDetails[]
-  updatedAt     DateTime                @updatedAt
+  contractMeters ContractMeter[]         @relation("ContractMeters")
+  createdAt      DateTime                @default(now())
+  updatedAt      DateTime                @updatedAt
 }
 
 model MeterReading {
@@ -430,7 +437,8 @@ model MeterReading {
   meterId       Int
   meter         Meter              @relation(fields: [meterId], references: [id], onDelete: Cascade)
   readingDate   DateTime
-  value         Float
+  value         Float // Bei Eintarif: Gesamtwert. Bei Zweitarif: HT-Wert
+  valueNt       Float? // Nur bei Zweitarif: NT-Wert (Niedertarif)
   unit          String             @default("kWh")
   notes         String?
   // Meldung & Übertragung
@@ -709,20 +717,38 @@ enum InvoiceType {
 }
 
 model EnergyContractDetails {
-  id                     Int       @id @default(autoincrement())
+  id                     Int             @id @default(autoincrement())
-  contractId             Int       @unique
+  contractId             Int             @unique
-  contract               Contract  @relation(fields: [contractId], references: [id], onDelete: Cascade)
+  contract               Contract        @relation(fields: [contractId], references: [id], onDelete: Cascade)
   meterId                Int?
-  meter                  Meter?    @relation(fields: [meterId], references: [id])
+  meter                  Meter?          @relation(fields: [meterId], references: [id])
   maloId                 String? // Marktlokations-ID
   annualConsumption      Float? // kWh für Strom, m³ für Gas
   annualConsumptionKwh   Float? // kWh für Gas (zusätzlich zu m³)
   basePrice              Float? // €/Monat
-  unitPrice              Float? // €/kWh (Arbeitspreis)
+  unitPrice              Float? // €/kWh (Arbeitspreis) - bei HT/NT: HT-Preis
+  unitPriceNt            Float? // €/kWh NT-Preis (nur bei Zweitarifzähler)
   bonus                  Float?
   previousProviderName   String?
   previousCustomerNumber String?
   invoices               Invoice[] // Rechnungen
+  contractMeters         ContractMeter[] // Zähler-Zuordnungen (inkl. Folgezähler)
+}
+
+model ContractMeter {
+  id                      Int                   @id @default(autoincrement())
+  energyContractDetailsId Int
+  energyContractDetails   EnergyContractDetails @relation(fields: [energyContractDetailsId], references: [id], onDelete: Cascade)
+  meterId                 Int
+  meter                   Meter                 @relation("ContractMeters", fields: [meterId], references: [id])
+  position                Int                   @default(0) // 0 = Original, 1 = erster Folgezähler, etc.
+  installedAt             DateTime? // Ab wann wird dieser Zähler am Vertrag genutzt?
+  removedAt               DateTime? // Wann wurde der Zähler gewechselt? (null = aktuell)
+  finalReading            Float? // Letzter Stand vor dem Wechsel
+  createdAt               DateTime              @default(now())
+
+  @@unique([energyContractDetailsId, meterId])
+  @@index([energyContractDetailsId])
 }
 
 model Invoice {

backend/node_modules/.prisma/client/wasm.js

@@ -361,6 +361,7 @@ exports.Prisma.MeterScalarFieldEnum = {
   customerId: 'customerId',
   meterNumber: 'meterNumber',
   type: 'type',
+  tariffModel: 'tariffModel',
   location: 'location',
   isActive: 'isActive',
   createdAt: 'createdAt',
@@ -372,6 +373,7 @@ exports.Prisma.MeterReadingScalarFieldEnum = {
   meterId: 'meterId',
   readingDate: 'readingDate',
   value: 'value',
+  valueNt: 'valueNt',
   unit: 'unit',
   notes: 'notes',
   reportedBy: 'reportedBy',
@@ -529,11 +531,23 @@ exports.Prisma.EnergyContractDetailsScalarFieldEnum = {
   annualConsumptionKwh: 'annualConsumptionKwh',
   basePrice: 'basePrice',
   unitPrice: 'unitPrice',
+  unitPriceNt: 'unitPriceNt',
   bonus: 'bonus',
   previousProviderName: 'previousProviderName',
   previousCustomerNumber: 'previousCustomerNumber'
 };
 
+exports.Prisma.ContractMeterScalarFieldEnum = {
+  id: 'id',
+  energyContractDetailsId: 'energyContractDetailsId',
+  meterId: 'meterId',
+  position: 'position',
+  installedAt: 'installedAt',
+  removedAt: 'removedAt',
+  finalReading: 'finalReading',
+  createdAt: 'createdAt'
+};
+
 exports.Prisma.InvoiceScalarFieldEnum = {
   id: 'id',
   energyContractDetailsId: 'energyContractDetailsId',
@@ -742,6 +756,11 @@ exports.MeterType = exports.$Enums.MeterType = {
   GAS: 'GAS'
 };
 
+exports.MeterTariffModel = exports.$Enums.MeterTariffModel = {
+  SINGLE: 'SINGLE',
+  DUAL: 'DUAL'
+};
+
 exports.MeterReadingStatus = exports.$Enums.MeterReadingStatus = {
   RECORDED: 'RECORDED',
   REPORTED: 'REPORTED',
@@ -855,6 +874,7 @@ exports.Prisma.ModelName = {
   ContractTask: 'ContractTask',
   ContractTaskSubtask: 'ContractTaskSubtask',
   EnergyContractDetails: 'EnergyContractDetails',
+  ContractMeter: 'ContractMeter',
   Invoice: 'Invoice',
   InternetContractDetails: 'InternetContractDetails',
   PhoneNumber: 'PhoneNumber',

backend/prisma/schema.prisma

@@ -411,17 +411,24 @@ enum MeterType {
   GAS
 }
 
+enum MeterTariffModel {
+  SINGLE       // Eintarifzähler (Standard)
+  DUAL         // Zweitarifzähler (HT/NT)
+}
+
 model Meter {
-  id            Int            @id @default(autoincrement())
+  id            Int              @id @default(autoincrement())
   customerId    Int
-  customer      Customer       @relation(fields: [customerId], references: [id], onDelete: Cascade)
+  customer      Customer         @relation(fields: [customerId], references: [id], onDelete: Cascade)
   meterNumber   String
   type          MeterType
+  tariffModel   MeterTariffModel @default(SINGLE)  // Eintarif oder Zweitarif (HT/NT)
   location      String?
-  isActive      Boolean        @default(true)
+  isActive      Boolean          @default(true)
-  readings      MeterReading[]
+  readings        MeterReading[]
-  energyDetails EnergyContractDetails[]
+  energyDetails   EnergyContractDetails[]
-  createdAt     DateTime       @default(now())
+  contractMeters  ContractMeter[] @relation("ContractMeters")
+  createdAt       DateTime       @default(now())
   updatedAt     DateTime       @updatedAt
 }
 
@@ -430,7 +437,8 @@ model MeterReading {
   meterId     Int
   meter       Meter                  @relation(fields: [meterId], references: [id], onDelete: Cascade)
   readingDate DateTime
-  value       Float
+  value       Float                  // Bei Eintarif: Gesamtwert. Bei Zweitarif: HT-Wert
+  valueNt     Float?                 // Nur bei Zweitarif: NT-Wert (Niedertarif)
   unit        String                 @default("kWh")
   notes       String?
   // Meldung & Übertragung
@@ -718,11 +726,29 @@ model EnergyContractDetails {
   annualConsumption      Float?    // kWh für Strom, m³ für Gas
   annualConsumptionKwh   Float?    // kWh für Gas (zusätzlich zu m³)
   basePrice              Float?    // €/Monat
-  unitPrice              Float?    // €/kWh (Arbeitspreis)
+  unitPrice              Float?    // €/kWh (Arbeitspreis) - bei HT/NT: HT-Preis
+  unitPriceNt            Float?    // €/kWh NT-Preis (nur bei Zweitarifzähler)
   bonus                  Float?
   previousProviderName   String?
   previousCustomerNumber String?
   invoices               Invoice[] // Rechnungen
+  contractMeters         ContractMeter[] // Zähler-Zuordnungen (inkl. Folgezähler)
+}
+
+model ContractMeter {
+  id                      Int                   @id @default(autoincrement())
+  energyContractDetailsId Int
+  energyContractDetails   EnergyContractDetails @relation(fields: [energyContractDetailsId], references: [id], onDelete: Cascade)
+  meterId                 Int
+  meter                   Meter                 @relation("ContractMeters", fields: [meterId], references: [id])
+  position                Int                   @default(0)    // 0 = Original, 1 = erster Folgezähler, etc.
+  installedAt             DateTime?              // Ab wann wird dieser Zähler am Vertrag genutzt?
+  removedAt               DateTime?              // Wann wurde der Zähler gewechselt? (null = aktuell)
+  finalReading            Float?                 // Letzter Stand vor dem Wechsel
+  createdAt               DateTime              @default(now())
+
+  @@unique([energyContractDetailsId, meterId])
+  @@index([energyContractDetailsId])
 }
 
 model Invoice {

backend/src/controllers/contract.controller.ts

@@ -244,6 +244,79 @@ export async function getCockpit(req: AuthRequest, res: Response): Promise<void>
   }
 }
 
+// ==================== FOLGEZÄHLER ====================
+
+export async function addSuccessorMeter(req: AuthRequest, res: Response): Promise<void> {
+  try {
+    const contractId = parseInt(req.params.id);
+    const { meterId, installedAt, finalReadingPrevious } = req.body;
+
+    const contract = await prisma.contract.findUnique({
+      where: { id: contractId },
+      include: { energyDetails: { include: { contractMeters: { orderBy: { position: 'asc' } } } } },
+    });
+
+    if (!contract?.energyDetails) {
+      res.status(404).json({ success: false, error: 'Energievertrag nicht gefunden' } as ApiResponse);
+      return;
+    }
+
+    const ecdId = contract.energyDetails.id;
+    const existingMeters = contract.energyDetails.contractMeters;
+    const nextPosition = existingMeters.length > 0
+      ? Math.max(...existingMeters.map(m => m.position)) + 1
+      : 0;
+
+    // Vorherigen Zähler als gewechselt markieren
+    if (existingMeters.length > 0 && finalReadingPrevious !== undefined) {
+      const prevMeter = existingMeters[existingMeters.length - 1];
+      await prisma.contractMeter.update({
+        where: { id: prevMeter.id },
+        data: {
+          removedAt: installedAt ? new Date(installedAt) : new Date(),
+          finalReading: parseFloat(finalReadingPrevious),
+        },
+      });
+    }
+
+    const contractMeter = await prisma.contractMeter.create({
+      data: {
+        energyContractDetailsId: ecdId,
+        meterId: parseInt(meterId),
+        position: nextPosition,
+        installedAt: installedAt ? new Date(installedAt) : new Date(),
+      },
+      include: { meter: { include: { readings: true } } },
+    });
+
+    // Aktuellen Zähler am Vertrag aktualisieren
+    await prisma.energyContractDetails.update({
+      where: { id: ecdId },
+      data: { meterId: parseInt(meterId) },
+    });
+
+    res.json({ success: true, data: contractMeter } as ApiResponse);
+  } catch (error) {
+    res.status(400).json({
+      success: false,
+      error: error instanceof Error ? error.message : 'Fehler beim Hinzufügen des Folgezählers',
+    } as ApiResponse);
+  }
+}
+
+export async function removeContractMeter(req: AuthRequest, res: Response): Promise<void> {
+  try {
+    const contractMeterId = parseInt(req.params.contractMeterId);
+    await prisma.contractMeter.delete({ where: { id: contractMeterId } });
+    res.json({ success: true, data: null } as ApiResponse);
+  } catch (error) {
+    res.status(400).json({
+      success: false,
+      error: error instanceof Error ? error.message : 'Fehler beim Entfernen',
+    } as ApiResponse);
+  }
+}
+
 // ==================== SNOOZE (VERTRAG ZURÜCKSTELLEN) ====================
 
 export async function snoozeContract(req: Request, res: Response): Promise<void> {

backend/src/controllers/customer.controller.ts

@@ -293,7 +293,14 @@ export async function getMeterReadings(req: Request, res: Response): Promise<voi
 
 export async function addMeterReading(req: Request, res: Response): Promise<void> {
   try {
-    const reading = await customerService.addMeterReading(parseInt(req.params.meterId), req.body);
+    const { readingDate, value, valueNt, unit, notes } = req.body;
+    const reading = await customerService.addMeterReading(parseInt(req.params.meterId), {
+      readingDate: new Date(readingDate),
+      value: parseFloat(value),
+      valueNt: valueNt !== undefined && valueNt !== null && valueNt !== '' ? parseFloat(valueNt) : undefined,
+      unit,
+      notes,
+    });
     res.status(201).json({ success: true, data: reading } as ApiResponse);
   } catch (error) {
     res.status(400).json({
@@ -305,10 +312,18 @@ export async function addMeterReading(req: Request, res: Response): Promise<void
 
 export async function updateMeterReading(req: Request, res: Response): Promise<void> {
   try {
+    const { readingDate, value, valueNt, unit, notes } = req.body;
+    const updateData: Record<string, unknown> = {};
+    if (readingDate !== undefined) updateData.readingDate = new Date(readingDate);
+    if (value !== undefined) updateData.value = parseFloat(value);
+    if (valueNt !== undefined) updateData.valueNt = valueNt !== null && valueNt !== '' ? parseFloat(valueNt) : null;
+    if (unit !== undefined) updateData.unit = unit;
+    if (notes !== undefined) updateData.notes = notes;
+
     const reading = await customerService.updateMeterReading(
       parseInt(req.params.meterId),
       parseInt(req.params.readingId),
-      req.body
+      updateData as any
     );
     res.json({ success: true, data: reading } as ApiResponse);
   } catch (error) {
@@ -358,15 +373,20 @@ export async function reportMeterReading(req: AuthRequest, res: Response): Promi
       return;
     }
 
-    const reading = await prisma.meterReading.create({
+    const parsedDate = readingDate ? new Date(readingDate) : new Date();
-      data: {
+    const parsedValue = parseFloat(value);
-        meterId,
+
-        value: parseFloat(value),
+    // Validierung über den Service (monoton steigend)
-        readingDate: readingDate ? new Date(readingDate) : new Date(),
+    const reading = await customerService.addMeterReading(meterId, {
-        notes,
+      readingDate: parsedDate,
-        reportedBy: user.email,
+      value: parsedValue,
-        status: 'REPORTED',
+      notes,
-      },
+    });
+
+    // Status auf REPORTED setzen
+    await prisma.meterReading.update({
+      where: { id: reading.id },
+      data: { reportedBy: user.email, status: 'REPORTED' },
     });
 
     res.status(201).json({ success: true, data: reading } as ApiResponse);

backend/src/middleware/audit.ts

@@ -24,6 +24,9 @@ const RESOURCE_MAPPING: Record<string, { type: string; extractId?: (req: AuthReq
   '/api/contract-durations': { type: 'ContractDuration', extractId: (req) => req.params.id },
   '/api/settings': { type: 'AppSetting', extractId: (req) => req.params.key },
   '/api/email-providers': { type: 'EmailProviderConfig', extractId: (req) => req.params.id },
+  '/api/meters': { type: 'Meter', extractId: (req) => req.params.id || req.params.meterId },
+  '/api/upload': { type: 'Upload' },
+  '/api/email-logs': { type: 'EmailLog' },
   '/api/auth': { type: 'Authentication' },
   '/api/audit-logs': { type: 'AuditLog', extractId: (req) => req.params.id },
   '/api/gdpr': { type: 'GDPR' },
@@ -116,6 +119,240 @@ function getClientIp(req: AuthRequest): string {
   return req.socket.remoteAddress || 'unknown';
 }
 
+// Menschenlesbare Bezeichnungen für Resource-Typen
+const RESOURCE_TYPE_LABELS: Record<string, string> = {
+  Customer: 'Kunde',
+  Contract: 'Vertrag',
+  BankCard: 'Bankverbindung',
+  IdentityDocument: 'Ausweis',
+  Address: 'Adresse',
+  Meter: 'Zähler',
+  MeterReading: 'Zählerstand',
+  User: 'Benutzer',
+  Provider: 'Anbieter',
+  Tariff: 'Tarif',
+  SalesPlatform: 'Vertriebsplattform',
+  ContractCategory: 'Vertragskategorie',
+  CancellationPeriod: 'Kündigungsfrist',
+  ContractDuration: 'Vertragslaufzeit',
+  EmailProviderConfig: 'E-Mail-Provider',
+  AppSetting: 'Einstellung',
+  CustomerConsent: 'Einwilligung',
+  ContractTask: 'Aufgabe',
+  ContractHistoryEntry: 'Vertragshistorie',
+  GDPR: 'Datenschutz',
+  Authentication: 'Anmeldung',
+  AuditLog: 'Audit-Protokoll',
+  StressfreiEmail: 'Stressfrei-E-Mail',
+  CachedEmail: 'E-Mail',
+};
+
+const ACTION_LABELS: Record<string, string> = {
+  CREATE: 'erstellt',
+  READ: 'aufgerufen',
+  UPDATE: 'aktualisiert',
+  DELETE: 'gelöscht',
+  EXPORT: 'exportiert',
+  ANONYMIZE: 'anonymisiert',
+  LOGIN: 'angemeldet',
+  LOGOUT: 'abgemeldet',
+  LOGIN_FAILED: 'Anmeldung fehlgeschlagen',
+};
+
+/**
+ * Erzeugt ein menschenlesbares Label für den Audit-Log-Eintrag
+ */
+function generateHumanLabel(
+  action: AuditAction,
+  resourceType: string,
+  req: AuthRequest,
+  responseBody: unknown
+): string {
+  const typeName = RESOURCE_TYPE_LABELS[resourceType] || resourceType;
+  const actionName = ACTION_LABELS[action] || action;
+
+  // Identifikator aus Response oder Request extrahieren
+  let identifier = '';
+  if (responseBody && typeof responseBody === 'object' && 'data' in responseBody) {
+    const data = (responseBody as { data: Record<string, unknown> }).data;
+    if (data) {
+      identifier =
+        (data.contractNumber as string) ||
+        (data.customerNumber as string) ||
+        (data.meterNumber as string) ||
+        (data.name as string) ||
+        (data.email as string) ||
+        (data.firstName && data.lastName ? `${data.firstName} ${data.lastName}` : '') ||
+        '';
+    }
+  }
+
+  // Spezial-Labels für bestimmte Endpunkte
+  const path = req.path;
+
+  // Auth
+  if (path.includes('/auth/login') || path.includes('/auth/customer-login')) {
+    const email = req.body?.email || '';
+    return action === 'LOGIN'
+      ? `Benutzer ${email} hat sich angemeldet`
+      : `Anmeldung fehlgeschlagen für ${email}`;
+  }
+  if (path.includes('/auth/logout')) return 'Benutzer hat sich abgemeldet';
+
+  // Kunden-Operationen
+  if (resourceType === 'Customer') {
+    if (action === 'CREATE') return `Kunde ${identifier} angelegt`;
+    if (action === 'UPDATE') return `Kundendaten ${identifier} aktualisiert`;
+    if (action === 'DELETE') return `Kunde ${identifier} gelöscht`;
+    if (action === 'READ' && req.params.id) return `Kundendaten ${identifier} aufgerufen`;
+    if (action === 'READ') return 'Kundenliste aufgerufen';
+  }
+
+  // Verträge
+  if (resourceType === 'Contract') {
+    if (path.includes('/cockpit')) return 'Vertrags-Cockpit aufgerufen';
+    if (path.includes('/follow-up')) return `Folgevertrag für ${identifier} erstellt`;
+    if (path.includes('/snooze')) return `Vertrag ${identifier} zurückgestellt`;
+    if (path.includes('/password')) return `Passwort für Vertrag ${identifier} abgerufen`;
+    if (path.includes('/sip-credentials')) return 'SIP-Zugangsdaten abgerufen';
+    if (path.includes('/internet-credentials')) return `Internet-Zugangsdaten für Vertrag ${identifier} abgerufen`;
+    if (path.includes('/successor-meter')) return `Folgezähler zu Vertrag ${identifier} hinzugefügt`;
+    if (action === 'CREATE') return `Vertrag ${identifier} angelegt`;
+    if (action === 'UPDATE') return `Vertrag ${identifier} aktualisiert`;
+    if (action === 'DELETE') return `Vertrag ${identifier} gelöscht`;
+    if (action === 'READ' && req.params.id) return `Vertrag ${identifier} aufgerufen`;
+    if (action === 'READ') return 'Vertragsliste aufgerufen';
+  }
+
+  // Bankverbindungen
+  if (resourceType === 'BankCard') {
+    if (action === 'CREATE') return `Bankverbindung hinzugefügt`;
+    if (action === 'UPDATE') return `Bankverbindung aktualisiert`;
+    if (action === 'DELETE') return `Bankverbindung gelöscht`;
+  }
+
+  // Ausweise
+  if (resourceType === 'IdentityDocument') {
+    if (action === 'CREATE') return `Ausweis ${identifier} hinzugefügt`;
+    if (action === 'UPDATE') return `Ausweis ${identifier} aktualisiert`;
+    if (action === 'DELETE') return `Ausweis gelöscht`;
+  }
+
+  // Adressen
+  if (resourceType === 'Address') {
+    if (action === 'CREATE') return `Adresse hinzugefügt`;
+    if (action === 'UPDATE') return `Adresse aktualisiert`;
+    if (action === 'DELETE') return `Adresse gelöscht`;
+  }
+
+  // Zähler
+  if (resourceType === 'Meter') {
+    if (action === 'CREATE') return `Zähler ${identifier} angelegt`;
+    if (action === 'UPDATE') return `Zähler ${identifier} aktualisiert`;
+    if (action === 'DELETE') return `Zähler gelöscht`;
+  }
+
+  // Einwilligungen
+  if (resourceType === 'CustomerConsent') {
+    const consentType = req.params.consentType || '';
+    const consentLabels: Record<string, string> = {
+      DATA_PROCESSING: 'Datenverarbeitung',
+      MARKETING_EMAIL: 'E-Mail-Marketing',
+      MARKETING_PHONE: 'Telefonmarketing',
+      DATA_SHARING_PARTNER: 'Datenweitergabe',
+    };
+    const consentName = consentLabels[consentType] || consentType;
+    if (action === 'UPDATE') {
+      const status = req.body?.status;
+      return status === 'GRANTED'
+        ? `Einwilligung "${consentName}" erteilt`
+        : `Einwilligung "${consentName}" widerrufen`;
+    }
+    if (action === 'READ') return 'Einwilligungen abgerufen';
+  }
+
+  // Benutzer
+  if (resourceType === 'User') {
+    if (action === 'CREATE') return `Benutzer ${identifier} angelegt`;
+    if (action === 'UPDATE') return `Benutzer ${identifier} aktualisiert`;
+    if (action === 'DELETE') return `Benutzer ${identifier} gelöscht`;
+    if (action === 'READ' && req.params.id) return `Benutzerdaten ${identifier} aufgerufen`;
+    if (action === 'READ') return 'Benutzerliste aufgerufen';
+  }
+
+  // Aufgaben
+  if (resourceType === 'ContractTask') {
+    if (path.includes('/complete')) return `Aufgabe als erledigt markiert`;
+    if (action === 'CREATE') return `Aufgabe erstellt`;
+    if (action === 'UPDATE') return `Aufgabe aktualisiert`;
+    if (action === 'DELETE') return `Aufgabe gelöscht`;
+  }
+
+  // E-Mail-Provider
+  if (resourceType === 'EmailProviderConfig') {
+    if (path.includes('/test-connection')) return `E-Mail-Provider Verbindungstest`;
+    if (path.includes('/provision')) return `E-Mail-Adresse provisioniert`;
+    if (action === 'CREATE') return `E-Mail-Provider ${identifier} angelegt`;
+    if (action === 'UPDATE') return `E-Mail-Provider ${identifier} aktualisiert`;
+    if (action === 'DELETE') return `E-Mail-Provider ${identifier} gelöscht`;
+  }
+
+  // GDPR
+  if (resourceType === 'GDPR') {
+    if (path.includes('/dashboard')) return 'DSGVO-Dashboard aufgerufen';
+    if (path.includes('/export')) return 'Kundendaten exportiert (DSGVO Art. 15)';
+    if (path.includes('/privacy-policy')) {
+      return action === 'UPDATE' ? 'Datenschutzerklärung aktualisiert' : 'Datenschutzerklärung aufgerufen';
+    }
+    if (path.includes('/authorization-template')) {
+      return action === 'UPDATE' ? 'Vollmacht-Vorlage aktualisiert' : 'Vollmacht-Vorlage aufgerufen';
+    }
+    if (path.includes('/send-consent-link')) return 'Datenschutz-Link versendet';
+    if (path.includes('/authorizations') && path.includes('/send')) return 'Vollmacht-Anfrage versendet';
+    if (path.includes('/authorizations') && path.includes('/grant')) return 'Vollmacht erteilt';
+    if (path.includes('/authorizations') && path.includes('/withdraw')) return 'Vollmacht widerrufen';
+    if (path.includes('/authorizations') && path.includes('/upload')) return 'Vollmacht-PDF hochgeladen';
+    if (path.includes('/authorizations') && path.includes('/document') && action === 'DELETE') return 'Vollmacht-PDF gelöscht';
+    if (path.includes('/my-privacy')) return 'Eigene Datenschutzseite aufgerufen';
+    if (path.includes('/my-consent-status')) return 'Eigener Einwilligungsstatus geprüft';
+    if (path.includes('/my-authorizations')) return 'Eigene Vollmachten aufgerufen';
+    if (path.includes('/deletions')) {
+      if (action === 'CREATE') return 'Löschanfrage erstellt';
+      if (path.includes('/process')) return 'Löschanfrage bearbeitet';
+      return 'Löschanfragen aufgerufen';
+    }
+    if (path.includes('/consent-status')) return 'Einwilligungsstatus geprüft';
+    if (path.includes('/consents/overview')) return 'Einwilligungsübersicht aufgerufen';
+  }
+
+  // Einstellungen
+  if (resourceType === 'AppSetting') {
+    if (action === 'UPDATE') return `Einstellung "${req.params.key || ''}" geändert`;
+    if (action === 'READ') return 'Einstellungen aufgerufen';
+  }
+
+  // Zähler-Readings
+  if (path.includes('/readings')) {
+    if (path.includes('/report')) return 'Zählerstand vom Kunden gemeldet';
+    if (path.includes('/transfer')) return 'Zählerstand als übertragen markiert';
+    if (action === 'CREATE') return 'Zählerstand erfasst';
+    if (action === 'UPDATE') return 'Zählerstand aktualisiert';
+    if (action === 'DELETE') return 'Zählerstand gelöscht';
+  }
+
+  // Upload-Operationen
+  if (path.includes('/upload') || path.includes('/privacy-policy')) {
+    if (path.includes('/privacy-policy') && action === 'DELETE') return 'Datenschutzerklärung-PDF gelöscht';
+    if (path.includes('/privacy-policy')) return 'Datenschutzerklärung-PDF hochgeladen';
+  }
+
+  // Standard-Fallback
+  if (identifier) {
+    return `${typeName} ${identifier} ${actionName}`;
+  }
+  return `${typeName} ${actionName}`;
+}
+
 /**
  * Audit Middleware - loggt alle API-Aufrufe asynchron
  */
@@ -162,22 +399,8 @@ export function auditMiddleware(req: AuthRequest, res: Response, next: NextFunct
         // Audit-Kontext abrufen (enthält Before/After-Werte von Prisma Middleware)
         const auditContext = getAuditContext();
 
-        // Label für bessere Lesbarkeit generieren
+        // Menschenlesbares Label generieren
-        let resourceLabel: string | undefined;
+        const resourceLabel = generateHumanLabel(action, mapping.type, req, responseBody);
-        if (responseBody && typeof responseBody === 'object' && 'data' in responseBody) {
-          const data = (responseBody as { data: Record<string, unknown> }).data;
-          if (data) {
-            // Versuche verschiedene Label-Felder
-            resourceLabel =
-              (data.contractNumber as string) ||
-              (data.customerNumber as string) ||
-              (data.name as string) ||
-              (data.email as string) ||
-              (data.firstName && data.lastName
-                ? `${data.firstName} ${data.lastName}`
-                : undefined);
-          }
-        }
 
         await createAuditLog({
           userId: req.user?.userId,

backend/src/routes/contract.routes.ts

@@ -20,6 +20,10 @@ router.post('/:id/follow-up', authenticate, requirePermission('contracts:create'
 // Snooze (Vertrag zurückstellen)
 router.patch('/:id/snooze', authenticate, requirePermission('contracts:update'), contractController.snoozeContract);
 
+// Folgezähler
+router.post('/:id/successor-meter', authenticate, requirePermission('contracts:update'), contractController.addSuccessorMeter);
+router.delete('/:id/contract-meter/:contractMeterId', authenticate, requirePermission('contracts:update'), contractController.removeContractMeter);
+
 // Get decrypted password
 router.get('/:id/password', authenticate, requirePermission('contracts:read'), contractController.getContractPassword);
 

backend/src/routes/upload.routes.ts

@@ -440,6 +440,16 @@ router.post(
         data: { privacyPolicyPath: relativePath },
       });
 
+      // Alle Consents auf GRANTED setzen (PDF = vollständige Einwilligung)
+      const consentTypes = ['DATA_PROCESSING', 'MARKETING_EMAIL', 'MARKETING_PHONE', 'DATA_SHARING_PARTNER'] as const;
+      for (const consentType of consentTypes) {
+        await prisma.customerConsent.upsert({
+          where: { customerId_consentType: { customerId, consentType } },
+          update: { status: 'GRANTED', grantedAt: new Date(), source: 'papier' },
+          create: { customerId, consentType, status: 'GRANTED', grantedAt: new Date(), source: 'papier', createdBy: (req as any).user?.email || 'admin' },
+        });
+      }
+
       res.json({
         success: true,
         data: {
@@ -488,6 +498,12 @@ router.delete(
         data: { privacyPolicyPath: null },
       });
 
+      // Nur Consents widerrufen die per Papier erteilt wurden
+      await prisma.customerConsent.updateMany({
+        where: { customerId, status: 'GRANTED', source: 'papier' },
+        data: { status: 'WITHDRAWN', withdrawnAt: new Date() },
+      });
+
       res.json({ success: true });
     } catch (error) {
       console.error('Delete error:', error);

backend/src/services/authorization.service.ts

@@ -146,13 +146,35 @@ export async function updateAuthorizationDocument(
  * Vollmacht-Dokument löschen
  */
 export async function deleteAuthorizationDocument(customerId: number, representativeId: number) {
+  // Prüfen ob die Vollmacht per Papier erteilt wurde
+  const auth = await prisma.representativeAuthorization.findUnique({
+    where: { customerId_representativeId: { customerId, representativeId } },
+    select: { source: true, documentPath: true },
+  });
+
+  if (!auth) throw new Error('Vollmacht nicht gefunden');
+
+  // Datei löschen
+  if (auth.documentPath) {
+    try {
+      const filePath = path.join(process.cwd(), auth.documentPath);
+      if (fs.existsSync(filePath)) {
+        fs.unlinkSync(filePath);
+      }
+    } catch (err) {
+      console.error('Fehler beim Löschen der Vollmacht-PDF:', err);
+    }
+  }
+
+  // Wenn per Papier erteilt → Vollmacht widerrufen
+  // Wenn per Portal/Online erteilt → nur PDF entfernen, Vollmacht bleibt
+  const withdrawData = auth.source === 'papier'
+    ? { documentPath: null, isGranted: false, withdrawnAt: new Date() }
+    : { documentPath: null };
+
   return prisma.representativeAuthorization.update({
-    where: {
+    where: { customerId_representativeId: { customerId, representativeId } },
-      customerId_representativeId: { customerId, representativeId },
+    data: withdrawData,
-    },
-    data: {
-      documentPath: null,
-    },
   });
 }
 

backend/src/services/contract.service.ts

@@ -125,14 +125,14 @@ export async function getContractById(id: number, decryptPassword = false) {
       previousProvider: true,
       previousContract: {
         include: {
-          energyDetails: { include: { meter: { include: { readings: true } }, invoices: true } },
+          energyDetails: { include: { meter: { include: { readings: true } }, contractMeters: { include: { meter: { include: { readings: true } } }, orderBy: { position: 'asc' as const } }, invoices: true } },
           internetDetails: { include: { phoneNumbers: true } },
           mobileDetails: { include: { simCards: true } },
           tvDetails: true,
           carInsuranceDetails: true,
         },
       },
-      energyDetails: { include: { meter: { include: { readings: true } }, invoices: true } },
+      energyDetails: { include: { meter: { include: { readings: true } }, contractMeters: { include: { meter: { include: { readings: true } } }, orderBy: { position: 'asc' as const } }, invoices: true } },
       internetDetails: { include: { phoneNumbers: true } },
       mobileDetails: { include: { simCards: true } },
       tvDetails: true,
@@ -403,11 +403,45 @@ export async function updateContract(
 
   // Update type-specific details
   if (energyDetails) {
+    const existingEcd = await prisma.energyContractDetails.findUnique({
+      where: { contractId: id },
+      select: { id: true, meterId: true },
+    });
+
     await prisma.energyContractDetails.upsert({
       where: { contractId: id },
       update: energyDetails,
       create: { contractId: id, ...energyDetails },
     });
+
+    // ContractMeter synchronisieren wenn sich der Zähler ändert
+    if (energyDetails.meterId !== undefined && existingEcd) {
+      const oldMeterId = existingEcd.meterId;
+      const newMeterId = energyDetails.meterId;
+
+      if (oldMeterId !== newMeterId) {
+        // Alle alten ContractMeter-Einträge entfernen
+        await prisma.contractMeter.deleteMany({
+          where: { energyContractDetailsId: existingEcd.id },
+        });
+
+        // Neuen ContractMeter-Eintrag erstellen (wenn ein Zähler gesetzt)
+        if (newMeterId) {
+          const contract = await prisma.contract.findUnique({
+            where: { id },
+            select: { startDate: true },
+          });
+          await prisma.contractMeter.create({
+            data: {
+              energyContractDetailsId: existingEcd.id,
+              meterId: newMeterId,
+              position: 0,
+              installedAt: contract?.startDate,
+            },
+          });
+        }
+      }
+    }
   }
 
   if (internetDetails) {

backend/src/services/contractCockpit.service.ts

@@ -89,6 +89,11 @@ export interface ReportedMeterReading {
     customerNumber: string;
     name: string;
   };
+  // Zugehöriger Vertrag
+  contract?: {
+    id: number;
+    contractNumber: string;
+  };
   // Anbieter-Info für Quick-Login
   providerPortal?: {
     providerName: string;
@@ -810,6 +815,7 @@ async function getReportedMeterReadings(): Promise<ReportedMeterReading[]> {
               contract: {
                 select: {
                   id: true,
+                  contractNumber: true,
                   portalUsername: true,
                   provider: {
                     select: { id: true, name: true, portalUrl: true },
@@ -847,6 +853,10 @@ async function getReportedMeterReadings(): Promise<ReportedMeterReading[]> {
         customerNumber: r.meter.customer.customerNumber,
         name: `${r.meter.customer.firstName} ${r.meter.customer.lastName}`,
       },
+      contract: contract ? {
+        id: contract.id,
+        contractNumber: contract.contractNumber,
+      } : undefined,
       providerPortal: provider?.portalUrl ? {
         providerName: provider.name,
         portalUrl: provider.portalUrl,

backend/src/services/customer.service.ts

@@ -443,6 +443,30 @@ export async function updateMeter(
 }
 
 export async function deleteMeter(id: number) {
+  // Prüfen ob der Zähler noch an Verträgen hängt
+  const linkedContracts = await prisma.contractMeter.findMany({
+    where: { meterId: id },
+    include: { energyContractDetails: { include: { contract: { select: { contractNumber: true } } } } },
+  });
+
+  if (linkedContracts.length > 0) {
+    const contractNumbers = linkedContracts
+      .map(cm => cm.energyContractDetails.contract.contractNumber)
+      .join(', ');
+    throw new Error(`Zähler kann nicht gelöscht werden – noch an Vertrag/Verträgen zugeordnet: ${contractNumbers}`);
+  }
+
+  // Auch direkte meterId-Referenz auf EnergyContractDetails prüfen
+  const directLinks = await prisma.energyContractDetails.findMany({
+    where: { meterId: id },
+    include: { contract: { select: { contractNumber: true } } },
+  });
+
+  if (directLinks.length > 0) {
+    const contractNumbers = directLinks.map(d => d.contract.contractNumber).join(', ');
+    throw new Error(`Zähler kann nicht gelöscht werden – noch an Vertrag/Verträgen zugeordnet: ${contractNumbers}`);
+  }
+
   return prisma.meter.delete({ where: { id } });
 }
 
@@ -451,14 +475,25 @@ export async function addMeterReading(
   data: {
     readingDate: Date;
     value: number;
+    valueNt?: number;
     unit?: string;
     notes?: string;
   }
 ) {
+  // Validierung: Zählerstand muss monoton steigend sein
+  await validateReadingValue(meterId, data.readingDate, data.value, undefined, 'HT');
+  if (data.valueNt !== undefined) {
+    await validateReadingValue(meterId, data.readingDate, data.valueNt, undefined, 'NT');
+  }
+
   return prisma.meterReading.create({
     data: {
       meterId,
-      ...data,
+      readingDate: data.readingDate,
+      value: data.value,
+      valueNt: data.valueNt,
+      unit: data.unit,
+      notes: data.notes,
     },
   });
 }
@@ -476,6 +511,7 @@ export async function updateMeterReading(
   data: {
     readingDate?: Date;
     value?: number;
+    valueNt?: number | null;
     unit?: string;
     notes?: string;
   }
@@ -489,12 +525,65 @@ export async function updateMeterReading(
     throw new Error('Zählerstand nicht gefunden');
   }
 
+  // Validierung bei Wertänderung
+  if (data.value !== undefined || data.readingDate !== undefined) {
+    await validateReadingValue(
+      meterId,
+      data.readingDate || reading.readingDate,
+      data.value ?? reading.value,
+      readingId,
+      'HT'
+    );
+  }
+  if (data.valueNt !== undefined || data.readingDate !== undefined) {
+    const ntVal = data.valueNt ?? reading.valueNt;
+    if (ntVal !== undefined && ntVal !== null) {
+      await validateReadingValue(
+        meterId,
+        data.readingDate || reading.readingDate,
+        ntVal,
+        readingId,
+        'NT'
+      );
+    }
+  }
+
   return prisma.meterReading.update({
     where: { id: readingId },
     data,
   });
 }
 
+/**
+ * Validiert, dass ein Zählerstand monoton steigend ist.
+ * tariffLabel: 'HT' für Hochtarif/Eintarif, 'NT' für Niedertarif
+ */
+async function validateReadingValue(meterId: number, readingDate: Date, value: number, excludeReadingId?: number, tariffLabel: 'HT' | 'NT' = 'HT') {
+  const existing = await prisma.meterReading.findMany({
+    where: { meterId, ...(excludeReadingId ? { id: { not: excludeReadingId } } : {}) },
+    orderBy: { readingDate: 'asc' },
+  });
+
+  const fmtDate = (d: Date) => d.toLocaleDateString('de-DE', { day: '2-digit', month: '2-digit', year: 'numeric' });
+  const fmtVal = (v: number) => v.toLocaleString('de-DE');
+  const label = tariffLabel === 'NT' ? 'NT-Zählerstand' : 'Zählerstand';
+
+  // Vergleichswert aus bestehendem Reading extrahieren
+  const getVal = (r: typeof existing[0]) => tariffLabel === 'NT' ? (r.valueNt ?? 0) : r.value;
+
+  // Stand vor dem neuen Datum
+  const before = [...existing].filter(r => r.readingDate <= readingDate).pop();
+  if (before && value < getVal(before)) {
+    throw new Error(`${label} (${fmtVal(value)}) darf nicht kleiner sein als der Stand vom ${fmtDate(before.readingDate)} (${fmtVal(getVal(before))})`);
+  }
+
+  // Stand nach dem neuen Datum
+  const after = existing.find(r => r.readingDate > readingDate);
+  if (after && value > getVal(after)) {
+    throw new Error(`${label} (${fmtVal(value)}) darf nicht größer sein als der spätere Stand vom ${fmtDate(after.readingDate)} (${fmtVal(getVal(after))})`);
+  }
+}
+
 export async function deleteMeterReading(meterId: number, readingId: number) {
   // Verify the reading belongs to the meter
   const reading = await prisma.meterReading.findFirst({

backend/todo.md

@@ -0,0 +1,34 @@
+Vertragliste bei Energie mit Anschlussadresse/Lieferadresse noch in der Liste
+Bei Mobilfunk die Mobilfunknummer und wenn vorhanden Karteninhaber
+Bei Festnetz, die Anschlussadresse/Lieferadresse
+Bei KFZ das Kennzeichen
+
+#erledigt
+Datenschutzerklärung wenn PDF hinterlegt wurde, alle Haken auf Grün setzten.
+Und wenn von Kunde im Kundenportal ein Haken weg, pdf wieder löschen und gesperrt setzen. bis endweder alle haken wieder gesetzt sind, oder pdf erneut hochgeladen
+Aktuell zählt das PDF als Alternative zu den Online-Haken. Du willst es so:
+
+PDF hochgeladen → alle 4 Online-Consents automatisch auf GRANTED setzen
+Kunde entfernt einen Haken im Portal → PDF löschen + Tabs sperren
+Entsperrung nur durch: alle Haken wieder setzen ODER neues PDF hochladen
+
+#erledigt
+Zweitarif (Gibt es auch 3 Tarifuzähler?) Zähler HT/NT bei Strom Zähler hinzufügen.
+Auch in die Berechnung die Verbäuche dann darstellen 
+
+
+Alle Datumsfelder mit 0 davor wenn es ne einstellige Zahl ist
+
+Jetzt : 1.1.2026
+Und gewollt 01.01.2026
+
+
+Die Auditmeldungen aussagekräftig
+
+
+Email Log und system testen
+
+
+Security System testen
+
+

frontend/src/pages/contracts/ContractCockpit.tsx

@@ -1,6 +1,7 @@
 import { useState, useMemo, useEffect, useRef } from 'react';
 import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
 import { Link, useSearchParams } from 'react-router-dom';
+import { pushHistory } from '../../utils/navigation';
 import { contractApi, meterApi } from '../../services/api';
 import Card from '../../components/ui/Card';
 import Badge from '../../components/ui/Badge';
@@ -282,7 +283,7 @@ export default function ContractCockpit() {
             <div className="flex items-center gap-2 flex-wrap">
               <Link
                 to={`/contracts/${contract.id}`}
-                state={{ from: '/contracts/cockpit' }}
+                state={pushHistory('/contracts/cockpit')}
                 className="font-medium hover:underline"
                 onClick={(e) => e.stopPropagation()}
               >
@@ -399,7 +400,7 @@ export default function ContractCockpit() {
 
             <Link
               to={`/contracts/${contract.id}`}
-              state={{ from: '/contracts/cockpit' }}
+              state={pushHistory('/contracts/cockpit')}
               className="p-2 hover:bg-white hover:bg-opacity-50 rounded"
               onClick={(e) => e.stopPropagation()}
               title="Zum Vertrag"
@@ -610,6 +611,15 @@ export default function ContractCockpit() {
                         {reading.customer.name}
                       </Link>
                       <span className="text-xs text-gray-500">({reading.customer.customerNumber})</span>
+                      {reading.contract && (
+                        <Link
+                          to={`/contracts/${reading.contract.id}`}
+                          state={pushHistory('/contracts/cockpit')}
+                          className="text-xs text-blue-600 hover:underline"
+                        >
+                          {reading.contract.contractNumber}
+                        </Link>
+                      )}
                     </div>
                     <p className="text-xs text-gray-600">
                       Zähler {reading.meter.meterNumber} – <strong>{reading.value} {reading.unit}</strong> am{' '}
@@ -635,6 +645,7 @@ export default function ContractCockpit() {
                     variant="secondary"
                     size="sm"
                     onClick={async () => {
+                      if (!confirm(`Zählerstand ${reading.value} ${reading.unit} (Zähler ${reading.meter.meterNumber}) als übertragen markieren?`)) return;
                       await meterApi.markTransferred(reading.meter.id, reading.id);
                       queryClient.invalidateQueries({ queryKey: ['contract-cockpit'] });
                     }}

frontend/src/pages/contracts/ContractDetail.tsx

@@ -1,5 +1,6 @@
 import { useState, useEffect } from 'react';
 import { useParams, Link, useNavigate, useLocation } from 'react-router-dom';
+import { pushHistory, popHistory } from '../../utils/navigation';
 import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
 import { contractApi, uploadApi, meterApi, contractTaskApi, appSettingsApi, gdprApi } from '../../services/api';
 import { ContractEmailsSection } from '../../components/email';
@@ -13,9 +14,9 @@ import Input from '../../components/ui/Input';
 import Modal from '../../components/ui/Modal';
 import FileUpload from '../../components/ui/FileUpload';
 import { Edit, Trash2, Copy, Eye, EyeOff, ArrowLeft, ArrowRight, Download, ExternalLink, Plus, ChevronDown, ChevronUp, Gauge, CheckCircle, Circle, ClipboardList, MessageSquare, Calculator, Info, X, BellOff, Lock, Shield } from 'lucide-react';
-import { calculateConsumption, calculateCosts } from '../../utils/energyCalculations';
+import { calculateConsumption, calculateCosts, calculateMultiMeterConsumption } from '../../utils/energyCalculations';
 import CopyButton, { CopyableBlock } from '../../components/ui/CopyButton';
-import type { ContractType, ContractStatus, SimCard, MeterReading, ContractTask, ContractTaskSubtask } from '../../types';
+import type { ContractType, ContractStatus, SimCard, MeterReading, ContractTask, ContractTaskSubtask, ContractMeter } from '../../types';
 
 const typeLabels: Record<ContractType, string> = {
   ELECTRICITY: 'Strom',
@@ -197,16 +198,19 @@ function SimCardDisplay({ simCard }: { simCard: SimCard }) {
 function MeterReadingsSection({
   meterId,
   meterType,
+  tariffModel,
   readings,
-  contractId,
   canEdit,
+  label,
 }: {
   meterId: number;
   meterType: 'ELECTRICITY' | 'GAS';
+  tariffModel?: string;
   readings: MeterReading[];
-  contractId: number;
   canEdit: boolean;
+  label?: string;
 }) {
+  const isDualTariff = tariffModel === 'DUAL';
   const [isExpanded, setIsExpanded] = useState(false);
   const [showAddModal, setShowAddModal] = useState(false);
   const [editingReading, setEditingReading] = useState<MeterReading | null>(null);
@@ -215,7 +219,7 @@ function MeterReadingsSection({
   const deleteReadingMutation = useMutation({
     mutationFn: (readingId: number) => meterApi.deleteReading(meterId, readingId),
     onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['contract', contractId.toString()] });
+      queryClient.invalidateQueries({ queryKey: ['contract'] });
     },
   });
 
@@ -231,7 +235,7 @@ function MeterReadingsSection({
       <div className="flex items-center justify-between mb-3">
         <div className="flex items-center gap-2">
           <Gauge className="w-4 h-4 text-gray-500" />
-          <h4 className="text-sm font-medium text-gray-700">Zählerstände</h4>
+          <h4 className="text-sm font-medium text-gray-700">{label || 'Zählerstände'}</h4>
           <Badge variant="default">{readings.length}</Badge>
         </div>
         <div className="flex items-center gap-2">
@@ -274,8 +278,12 @@ function MeterReadingsSection({
               </span>
               <div className="flex items-center gap-2">
                 <span className="font-mono flex items-center gap-1">
-                  {reading.value.toLocaleString('de-DE')} {reading.unit}
+                  {isDualTariff && reading.valueNt != null ? (
-                  <CopyButton value={reading.value.toString()} title="Nur Wert kopieren" />
+                    <>HT: {reading.value.toLocaleString('de-DE')} / NT: {reading.valueNt.toLocaleString('de-DE')} {reading.unit}</>
+                  ) : (
+                    <>{reading.value.toLocaleString('de-DE')} {reading.unit}</>
+                  )}
+                  <CopyButton value={reading.value.toString()} title="Wert kopieren" />
                 </span>
                 {canEdit && (
                   <div className="opacity-0 group-hover:opacity-100 flex gap-1">
@@ -324,9 +332,9 @@ function MeterReadingsSection({
             setEditingReading(null);
           }}
           meterId={meterId}
-          contractId={contractId}
           reading={editingReading}
           defaultUnit={defaultUnit}
+          tariffModel={tariffModel}
         />
       )}
     </div>
@@ -334,22 +342,135 @@ function MeterReadingsSection({
 }
 
 // Meter Reading Modal Component
+function SuccessorMeterButton({
+  contractId,
+  customerId,
+  meterType,
+  existingMeterIds,
+}: {
+  contractId: number;
+  customerId: number;
+  meterType: string;
+  existingMeterIds: number[];
+}) {
+  const [showForm, setShowForm] = useState(false);
+  const [selectedMeterId, setSelectedMeterId] = useState('');
+  const [installedAt, setInstalledAt] = useState(new Date().toISOString().split('T')[0]);
+  const [finalReading, setFinalReading] = useState('');
+  const queryClient = useQueryClient();
+
+  const { data: metersData } = useQuery({
+    queryKey: ['customer-meters', customerId],
+    queryFn: () => meterApi.getByCustomer(customerId),
+    enabled: showForm,
+  });
+
+  const addMutation = useMutation({
+    mutationFn: (data: { meterId: number; installedAt?: string; finalReadingPrevious?: number }) =>
+      contractApi.addSuccessorMeter(contractId, data),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['contract'] });
+      setShowForm(false);
+      setSelectedMeterId('');
+      setFinalReading('');
+    },
+  });
+
+  // Nur Zähler gleichen Typs anzeigen die noch nicht am Vertrag sind
+  const availableMeters = (metersData?.data || []).filter(
+    (m) => m.type === meterType && !existingMeterIds.includes(m.id) && m.isActive
+  );
+
+  if (!showForm) {
+    return (
+      <div className="mt-3 pt-3 border-t">
+        <Button variant="secondary" size="sm" onClick={() => setShowForm(true)}>
+          <Plus className="w-4 h-4 mr-1" />
+          Folgezähler hinzufügen
+        </Button>
+      </div>
+    );
+  }
+
+  return (
+    <div className="mt-3 pt-3 border-t bg-blue-50 rounded-lg p-4">
+      <h4 className="text-sm font-medium mb-3">Folgezähler hinzufügen (Zählerwechsel)</h4>
+      <div className="grid grid-cols-1 sm:grid-cols-3 gap-3">
+        <div>
+          <label className="block text-sm font-medium text-gray-700 mb-1">Neuer Zähler *</label>
+          <select
+            value={selectedMeterId}
+            onChange={(e) => setSelectedMeterId(e.target.value)}
+            className="block w-full px-3 py-2 border border-gray-300 rounded-lg text-sm"
+          >
+            <option value="">Bitte wählen...</option>
+            {availableMeters.map((m) => (
+              <option key={m.id} value={m.id}>
+                {m.meterNumber} {m.location ? `(${m.location})` : ''}
+              </option>
+            ))}
+          </select>
+          {availableMeters.length === 0 && (
+            <p className="text-xs text-amber-600 mt-1">Kein passender Zähler verfügbar. Bitte zuerst beim Kunden anlegen.</p>
+          )}
+        </div>
+        <Input
+          label="Wechseldatum"
+          type="date"
+          value={installedAt}
+          onChange={(e) => setInstalledAt(e.target.value)}
+        />
+        <Input
+          label="Letzter Stand alter Zähler"
+          type="number"
+          step="0.01"
+          value={finalReading}
+          onChange={(e) => setFinalReading(e.target.value)}
+          placeholder="Optional"
+        />
+      </div>
+      <div className="flex gap-2 mt-3">
+        <Button
+          size="sm"
+          onClick={() => addMutation.mutate({
+            meterId: parseInt(selectedMeterId),
+            installedAt,
+            finalReadingPrevious: finalReading ? parseFloat(finalReading) : undefined,
+          })}
+          disabled={!selectedMeterId || addMutation.isPending}
+        >
+          {addMutation.isPending ? 'Speichern...' : 'Hinzufügen'}
+        </Button>
+        <Button variant="secondary" size="sm" onClick={() => setShowForm(false)}>
+          Abbrechen
+        </Button>
+      </div>
+      {addMutation.isError && (
+        <p className="text-xs text-red-600 mt-2">
+          {addMutation.error instanceof Error ? addMutation.error.message : 'Fehler beim Hinzufügen'}
+        </p>
+      )}
+    </div>
+  );
+}
+
 function MeterReadingModal({
   isOpen,
   onClose,
   meterId,
-  contractId,
   reading,
   defaultUnit,
+  tariffModel,
 }: {
   isOpen: boolean;
   onClose: () => void;
   meterId: number;
-  contractId: number;
   reading?: MeterReading | null;
   defaultUnit: string;
+  tariffModel?: string;
 }) {
   const queryClient = useQueryClient();
+  const isDualTariff = tariffModel === 'DUAL';
   const isEditing = !!reading;
 
   const [formData, setFormData] = useState({
@@ -357,33 +478,47 @@ function MeterReadingModal({
       ? new Date(reading.readingDate).toISOString().split('T')[0]
       : new Date().toISOString().split('T')[0],
     value: reading?.value?.toString() || '',
+    valueNt: reading?.valueNt?.toString() || '',
     notes: reading?.notes || '',
   });
 
+  const [error, setError] = useState<string | null>(null);
+
   const createMutation = useMutation({
     mutationFn: (data: Partial<MeterReading>) => meterApi.addReading(meterId, data),
     onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['contract', contractId.toString()] });
+      queryClient.invalidateQueries({ queryKey: ['contract'] });
+      setError(null);
       onClose();
     },
+    onError: (err) => {
+      setError(err instanceof Error ? err.message : 'Fehler beim Speichern');
+    },
   });
 
   const updateMutation = useMutation({
     mutationFn: (data: Partial<MeterReading>) => meterApi.updateReading(meterId, reading!.id, data),
     onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['contract', contractId.toString()] });
+      queryClient.invalidateQueries({ queryKey: ['contract'] });
+      setError(null);
       onClose();
     },
+    onError: (err) => {
+      setError(err instanceof Error ? err.message : 'Fehler beim Speichern');
+    },
   });
 
   const handleSubmit = (e: React.FormEvent) => {
     e.preventDefault();
-    const data = {
+    const data: Record<string, unknown> = {
       readingDate: new Date(formData.readingDate),
       value: parseFloat(formData.value),
       unit: defaultUnit,
       notes: formData.notes || undefined,
     };
+    if (isDualTariff && formData.valueNt) {
+      data.valueNt = parseFloat(formData.valueNt);
+    }
     if (isEditing) {
       updateMutation.mutate(data as unknown as Partial<MeterReading>);
     } else {
@@ -404,10 +539,10 @@ function MeterReadingModal({
           required
         />
 
-        <div className="grid grid-cols-3 gap-4">
+        <div className={`grid ${isDualTariff ? 'grid-cols-2' : 'grid-cols-3'} gap-4`}>
-          <div className="col-span-2">
+          <div className={isDualTariff ? '' : 'col-span-2'}>
             <Input
-              label="Zählerstand"
+              label={isDualTariff ? 'HT-Stand (Hochtarif)' : 'Zählerstand'}
               type="number"
               step="0.01"
               value={formData.value}
@@ -415,12 +550,26 @@ function MeterReadingModal({
               required
             />
           </div>
-          <div>
+          {isDualTariff && (
-            <label className="block text-sm font-medium text-gray-700 mb-1">Einheit</label>
+            <div>
-            <div className="h-10 flex items-center px-3 bg-gray-100 border border-gray-300 rounded-md text-gray-700">
+              <Input
-              {defaultUnit}
+                label="NT-Stand (Niedertarif)"
+                type="number"
+                step="0.01"
+                value={formData.valueNt}
+                onChange={(e) => setFormData({ ...formData, valueNt: e.target.value })}
+                required
+              />
             </div>
-          </div>
+          )}
+          {!isDualTariff && (
+            <div>
+              <label className="block text-sm font-medium text-gray-700 mb-1">Einheit</label>
+              <div className="h-10 flex items-center px-3 bg-gray-100 border border-gray-300 rounded-md text-gray-700">
+                {defaultUnit}
+              </div>
+            </div>
+          )}
         </div>
 
         <Input
@@ -429,6 +578,12 @@ function MeterReadingModal({
           onChange={(e) => setFormData({ ...formData, notes: e.target.value })}
         />
 
+        {error && (
+          <div className="p-3 bg-red-50 border border-red-200 rounded-lg text-sm text-red-700">
+            {error}
+          </div>
+        )}
+
         <div className="flex justify-end gap-2 pt-4">
           <Button type="button" variant="secondary" onClick={onClose}>
             Abbrechen
@@ -450,24 +605,67 @@ function EnergyConsumptionCalculation({
   endDate,
   basePrice,
   unitPrice,
+  unitPriceNt,
   bonus,
+  hasMeter,
+  contractMeters,
 }: {
   contractType: 'ELECTRICITY' | 'GAS';
   readings: MeterReading[];
-  startDate: string;
+  startDate?: string;
-  endDate: string;
+  endDate?: string;
   basePrice?: number;
   unitPrice?: number;
   bonus?: number;
+  unitPriceNt?: number;
+  hasMeter?: boolean;
+  contractMeters?: ContractMeter[];
 }) {
-  // Berechnung durchführen
+  // Fehlende Felder ermitteln
-  const consumption = calculateConsumption(readings, startDate, endDate, contractType);
+  const missingFields: string[] = [];
-  const costs = consumption.consumptionKwh > 0
+  if (!startDate) missingFields.push('Vertragsbeginn');
-    ? calculateCosts(consumption.consumptionKwh, basePrice, unitPrice, bonus)
+  if (!endDate) missingFields.push('Vertragsende');
+  if (!hasMeter) missingFields.push('Zähler verknüpft');
+  if (basePrice == null) missingFields.push('Grundpreis');
+  if (unitPrice == null) missingFields.push('Arbeitspreis');
+
+  const hasRequiredDates = !!startDate && !!endDate;
+
+  // Alle Readings über alle Zähler zählen
+  const allReadingsCount = contractMeters && contractMeters.length > 0
+    ? contractMeters.reduce((sum, cm) => sum + (cm.meter?.readings?.length || 0), 0)
+    : readings.length;
+
+  if (hasRequiredDates && hasMeter && allReadingsCount < 2) {
+    missingFields.push(`Mindestens 2 Zählerstände im Vertragszeitraum (${allReadingsCount} vorhanden)`);
+  }
+
+  // Berechnung: Multi-Zähler wenn vorhanden, sonst Single
+  let consumption = null;
+  if (hasRequiredDates) {
+    if (contractMeters && contractMeters.length > 1) {
+      consumption = calculateMultiMeterConsumption(contractMeters, startDate!, endDate!, contractType);
+    } else {
+      consumption = calculateConsumption(readings, startDate!, endDate!, contractType);
+    }
+  }
+
+  const htKwh = consumption?.consumptionHt ?? consumption?.consumptionKwh ?? 0;
+  const ntKwh = consumption?.consumptionNt;
+  const costs = consumption && consumption.consumptionKwh > 0
+    ? calculateCosts(htKwh, basePrice, unitPrice, bonus, ntKwh, unitPriceNt)
     : null;
 
-  // Nichts anzeigen wenn keine Daten
+  const canCalculate = consumption && (consumption.type === 'exact' || consumption.type === 'projected');
-  if (consumption.type === 'none') return null;
+
+  // Wenn Berechnung fehlschlägt aber keine Felder fehlen → Hinweis aus der Berechnung anzeigen
+  if (!canCalculate && consumption && missingFields.length === 0) {
+    if (consumption.type === 'insufficient' && consumption.message) {
+      missingFields.push(consumption.message);
+    } else if (consumption.type === 'none') {
+      missingFields.push('Keine Zählerstände im Vertragszeitraum vorhanden');
+    }
+  }
 
   const formatNumber = (num: number, decimals: number = 2) =>
     num.toLocaleString('de-DE', { minimumFractionDigits: decimals, maximumFractionDigits: decimals });
@@ -481,40 +679,61 @@ function EnergyConsumptionCalculation({
       <div className="flex items-center gap-2 mb-3">
         <Calculator className="w-4 h-4 text-gray-500" />
         <h4 className="text-sm font-medium text-gray-700">Verbrauch & Kosten</h4>
-        {consumption.type === 'exact' && (
+        {canCalculate && consumption!.type === 'exact' && (
           <Badge variant="success">Exakt</Badge>
         )}
-        {consumption.type === 'projected' && (
+        {canCalculate && consumption!.type === 'projected' && (
           <Badge variant="warning">Hochrechnung</Badge>
         )}
       </div>
 
-      {/* Fall C: Unzureichende Daten */}
+      {/* Fehlende Daten */}
-      {consumption.type === 'insufficient' ? (
+      {!canCalculate ? (
-        <p className="text-sm text-gray-500 italic">{consumption.message}</p>
+        <div className="bg-gray-50 rounded-lg p-4">
+          <p className="text-sm text-gray-600 mb-3">
+            Für die Berechnung fehlen noch folgende Angaben:
+          </p>
+          <ul className="space-y-1.5">
+            {missingFields.map((field) => (
+              <li key={field} className="flex items-center gap-2 text-sm">
+                <Circle className="w-3 h-3 text-gray-300 flex-shrink-0" />
+                <span className="text-gray-500">{field}</span>
+              </li>
+            ))}
+          </ul>
+          {consumption?.type === 'insufficient' && (
+            <p className="text-sm text-amber-600 mt-3 italic">{consumption.message}</p>
+          )}
+        </div>
       ) : (
         <div className="bg-gray-50 rounded-lg p-4 space-y-4">
           {/* Verbrauchsanzeige */}
           <div>
             <h5 className="text-sm font-medium text-gray-600 mb-2">
               Berechneter Verbrauch
-              {consumption.type === 'projected' && ' (hochgerechnet)'}
+              {consumption!.type === 'projected' && ' (hochgerechnet)'}
             </h5>
             <div className="text-lg font-semibold text-gray-900">
               {contractType === 'GAS' ? (
                 <>
-                  <span className="font-mono">{formatNumber(consumption.consumptionM3 || 0)} m³</span>
+                  <span className="font-mono">{formatNumber(consumption!.consumptionM3 || 0)} m³</span>
                   <span className="text-gray-500 text-sm ml-2">
-                    = {formatNumber(consumption.consumptionKwh)} kWh
+                    = {formatNumber(consumption!.consumptionKwh)} kWh
                   </span>
                 </>
+              ) : consumption!.consumptionHt !== undefined && consumption!.consumptionNt !== undefined ? (
+                <div className="space-y-1">
+                  <div><span className="text-sm text-gray-500">HT:</span> <span className="font-mono">{formatNumber(consumption!.consumptionHt)} kWh</span></div>
+                  <div><span className="text-sm text-gray-500">NT:</span> <span className="font-mono">{formatNumber(consumption!.consumptionNt)} kWh</span></div>
+                  <div className="text-sm text-gray-500">Gesamt: {formatNumber(consumption!.consumptionKwh)} kWh</div>
+                </div>
               ) : (
-                <span className="font-mono">{formatNumber(consumption.consumptionKwh)} kWh</span>
+                <span className="font-mono">{formatNumber(consumption!.consumptionKwh)} kWh</span>
               )}
             </div>
-            {consumption.startReading && consumption.endReading && (
+            {consumption!.startReading && consumption!.endReading && (
               <p className="text-xs text-gray-400 mt-1">
-                Basierend auf Zählerständen vom {formatDate(consumption.startReading.readingDate)} bis {formatDate(consumption.endReading.readingDate)}
+                Basierend auf Zählerständen vom {formatDate(consumption!.startReading.readingDate)} bis {formatDate(consumption!.endReading.readingDate)}
               </p>
             )}
           </div>
@@ -533,15 +752,24 @@ function EnergyConsumptionCalculation({
                     <span className="font-mono">{formatNumber(costs.annualBaseCost)} €</span>
                   </div>
                 )}
-                {/* Arbeitspreis */}
+                {/* Arbeitspreis HT */}
                 {unitPrice != null && unitPrice > 0 && (
                   <div className="flex justify-between">
                     <span className="text-gray-600">
-                      Arbeitspreis: {formatNumber(consumption.consumptionKwh)} kWh × {formatNumber(unitPrice, 4)} €
+                      {costs.annualConsumptionCostNt ? 'HT-Arbeitspreis' : 'Arbeitspreis'}: {formatNumber(htKwh)} kWh × {formatNumber(unitPrice, 4)} €
                     </span>
                     <span className="font-mono">{formatNumber(costs.annualConsumptionCost)} €</span>
                   </div>
                 )}
+                {/* Arbeitspreis NT */}
+                {costs.annualConsumptionCostNt != null && costs.annualConsumptionCostNt > 0 && unitPriceNt && (
+                  <div className="flex justify-between">
+                    <span className="text-gray-600">
+                      NT-Arbeitspreis: {formatNumber(ntKwh || 0)} kWh × {formatNumber(unitPriceNt, 4)} €
+                    </span>
+                    <span className="font-mono">{formatNumber(costs.annualConsumptionCostNt)} €</span>
+                  </div>
+                )}
                 {/* Trennlinie */}
                 <div className="border-t border-gray-300 pt-2">
                   <div className="flex justify-between font-medium">
@@ -1212,7 +1440,7 @@ export default function ContractDetail() {
   const navigate = useNavigate();
   const location = useLocation();
   const queryClient = useQueryClient();
-  const backTo = (location.state as any)?.from as string | undefined;
+  const currentPath = `/contracts/${id}`;
   const { hasPermission, isCustomer, isCustomerPortal } = useAuth();
   const contractId = parseInt(id!);
 
@@ -1424,13 +1652,15 @@ export default function ContractDetail() {
   }
 
   const c = data.data;
+  const fallbackBack = isCustomerPortal ? '/contracts' : (c.customer ? `/customers/${c.customer.id}?tab=contracts` : '/contracts');
+  const back = popHistory(location.state, fallbackBack);
 
   // Consent-Sperrung: Vertrag nicht anzeigen wenn Kunde keine Einwilligung hat
   if (!hasConsentApproval) {
     return (
       <div>
         <div className="flex items-center gap-4 mb-6">
-          <Button variant="ghost" size="sm" onClick={() => navigate(backTo || (isCustomerPortal ? '/contracts' : (c.customer ? `/customers/${c.customer.id}?tab=contracts` : '/contracts')))}>
+          <Button variant="ghost" size="sm" onClick={() => navigate(back.to, { state: back.state })}>
             <ArrowLeft className="w-4 h-4" />
           </Button>
           <h1 className="text-2xl font-bold">Vertrag {c.contractNumber}</h1>
@@ -1465,7 +1695,7 @@ export default function ContractDetail() {
             <Button
               variant="ghost"
               size="sm"
-              onClick={() => navigate(backTo || (isCustomerPortal ? '/contracts' : (c.customer ? `/customers/${c.customer.id}?tab=contracts` : '/contracts')))}
+              onClick={() => navigate(back.to, { state: back.state })}
             >
               <ArrowLeft className="w-4 h-4" />
             </Button>
@@ -1499,7 +1729,7 @@ export default function ContractDetail() {
           {c.customer && (
             <p className="text-gray-500 ml-10">
               Kunde:{' '}
-              <Link to={`/customers/${c.customer.id}`} state={{ from: `/contracts/${id}` }} className="text-blue-600 hover:underline">
+              <Link to={`/customers/${c.customer.id}`} state={pushHistory(currentPath, location.state)} className="text-blue-600 hover:underline">
                 {c.customer.companyName || `${c.customer.firstName} ${c.customer.lastName}`}
               </Link>
             </p>
@@ -1534,7 +1764,7 @@ export default function ContractDetail() {
               </Link>
             )}
             {hasPermission('contracts:update') && (
-              <Link to={`/contracts/${id}/edit`} state={{ from: `/contracts/${id}` }}>
+              <Link to={`/contracts/${id}/edit`} state={pushHistory(currentPath, location.state)}>
                 <Button variant="secondary">
                   <Edit className="w-4 h-4 mr-2" />
                   Bearbeiten
@@ -2201,7 +2431,12 @@ export default function ContractDetail() {
           <dl className="grid grid-cols-2 md:grid-cols-4 gap-4">
             {c.energyDetails.meter && (
               <div>
-                <dt className="text-sm text-gray-500">Zählernummer</dt>
+                <dt className="text-sm text-gray-500 flex items-center gap-1">
+                  Zählernummer
+                  {c.energyDetails.meter.tariffModel === 'DUAL' && (
+                    <Badge variant="default">HT/NT</Badge>
+                  )}
+                </dt>
                 <dd className="font-mono flex items-center gap-1">
                   {c.energyDetails.meter.meterNumber}
                   <CopyButton value={c.energyDetails.meter.meterNumber} />
@@ -2242,12 +2477,22 @@ export default function ContractDetail() {
             )}
             {c.energyDetails.unitPrice != null && (
               <div>
-                <dt className="text-sm text-gray-500">Arbeitspreis</dt>
+                <dt className="text-sm text-gray-500">
+                  {c.energyDetails.unitPriceNt != null ? 'HT-Arbeitspreis' : 'Arbeitspreis'}
+                </dt>
                 <dd>
                   {c.energyDetails.unitPrice.toLocaleString('de-DE', { minimumFractionDigits: 2, maximumFractionDigits: 10 })} €/kWh
                 </dd>
               </div>
             )}
+            {c.energyDetails.unitPriceNt != null && (
+              <div>
+                <dt className="text-sm text-gray-500">NT-Arbeitspreis</dt>
+                <dd>
+                  {c.energyDetails.unitPriceNt.toLocaleString('de-DE', { minimumFractionDigits: 2, maximumFractionDigits: 10 })} €/kWh
+                </dd>
+              </div>
+            )}
             {c.energyDetails.bonus && (
               <div>
                 <dt className="text-sm text-gray-500">Bonus</dt>
@@ -2271,29 +2516,58 @@ export default function ContractDetail() {
             )}
           </dl>
 
-          {/* Zählerstände */}
+          {/* Zählerstände - Multi-Zähler Support */}
-          {c.energyDetails.meter && (
+          {c.energyDetails.contractMeters && c.energyDetails.contractMeters.length > 0 ? (
+            <>
+              {c.energyDetails.contractMeters.map((cm: ContractMeter, idx: number) => (
+                cm.meter && (
+                  <MeterReadingsSection
+                    key={cm.id}
+                    meterId={cm.meter.id}
+                    meterType={cm.meter.type}
+                    tariffModel={cm.meter.tariffModel}
+                    readings={cm.meter.readings || []}
+                    canEdit={hasPermission('contracts:update') && !isCustomer}
+                    label={c.energyDetails!.contractMeters!.length > 1
+                      ? `Zähler ${idx + 1}: ${cm.meter.meterNumber}${cm.removedAt ? ' (gewechselt)' : ' (aktuell)'}`
+                      : undefined
+                    }
+                  />
+                )
+              ))}
+              {/* Folgezähler hinzufügen */}
+              {hasPermission('contracts:update') && !isCustomer && (
+                <SuccessorMeterButton
+                  contractId={contractId}
+                  customerId={c.customerId}
+                  meterType={c.type as 'ELECTRICITY' | 'GAS'}
+                  existingMeterIds={c.energyDetails.contractMeters.map((cm: ContractMeter) => cm.meterId)}
+                />
+              )}
+            </>
+          ) : c.energyDetails.meter ? (
             <MeterReadingsSection
               meterId={c.energyDetails.meter.id}
               meterType={c.energyDetails.meter.type}
+              tariffModel={c.energyDetails.meter.tariffModel}
               readings={c.energyDetails.meter.readings || []}
-              contractId={contractId}
               canEdit={hasPermission('contracts:update') && !isCustomer}
             />
-          )}
+          ) : null}
 
           {/* Verbrauchsberechnung & Kostenvorschau */}
-          {c.energyDetails.meter && c.startDate && c.endDate && (
+          <EnergyConsumptionCalculation
-            <EnergyConsumptionCalculation
+            contractType={c.type as 'ELECTRICITY' | 'GAS'}
-              contractType={c.type as 'ELECTRICITY' | 'GAS'}
+            readings={c.energyDetails.meter?.readings || []}
-              readings={c.energyDetails.meter.readings || []}
+            startDate={c.startDate}
-              startDate={c.startDate}
+            endDate={c.endDate}
-              endDate={c.endDate}
+            basePrice={c.energyDetails.basePrice}
-              basePrice={c.energyDetails.basePrice}
+            unitPrice={c.energyDetails.unitPrice}
-              unitPrice={c.energyDetails.unitPrice}
+            unitPriceNt={c.energyDetails.unitPriceNt}
-              bonus={c.energyDetails.bonus}
+            bonus={c.energyDetails.bonus}
-            />
+            hasMeter={!!c.energyDetails.meter}
-          )}
+            contractMeters={c.energyDetails.contractMeters}
+          />
 
           {/* Rechnungen */}
           <InvoicesSection

frontend/src/pages/contracts/ContractForm.tsx

@@ -1,5 +1,6 @@
 import { useEffect, useState } from 'react';
 import { useNavigate, useParams, useSearchParams, useLocation } from 'react-router-dom';
+import { popHistory } from '../../utils/navigation';
 import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
 import { useForm } from 'react-hook-form';
 import { contractApi, customerApi, platformApi, cancellationPeriodApi, contractDurationApi, providerApi, contractCategoryApi } from '../../services/api';
@@ -64,7 +65,7 @@ export default function ContractForm() {
   const location = useLocation();
   const queryClient = useQueryClient();
   const isEdit = !!id;
-  const backTo = (location.state as any)?.from as string | undefined;
+  const back = popHistory(location.state, isEdit ? `/contracts/${id}` : '/contracts');
 
   const preselectedCustomerId = searchParams.get('customerId');
 
@@ -80,6 +81,7 @@ export default function ContractForm() {
   const contractType = watch('type') as ContractType;
   const customerId = watch('customerId');
   const previousContractId = watch('previousContractId');
+  const selectedMeterId = watch('meterId');
 
   // Fetch existing contract for edit
   const { data: contract } = useQuery({
@@ -276,6 +278,7 @@ export default function ContractForm() {
         annualConsumptionKwh: c.energyDetails?.annualConsumptionKwh || '',
         basePrice: c.energyDetails?.basePrice || '',
         unitPrice: c.energyDetails?.unitPrice || '',
+        unitPriceNt: c.energyDetails?.unitPriceNt || '',
         bonus: c.energyDetails?.bonus || '',
         // Internet details
         downloadSpeed: c.internetDetails?.downloadSpeed || '',
@@ -512,6 +515,7 @@ export default function ContractForm() {
         annualConsumptionKwh: data.annualConsumptionKwh ? parseFloat(data.annualConsumptionKwh) : null,
         basePrice: data.basePrice ? parseFloat(data.basePrice) : null,
         unitPrice: data.unitPrice ? parseFloat(data.unitPrice) : null,
+        unitPriceNt: data.unitPriceNt ? parseFloat(data.unitPriceNt) : null,
         bonus: data.bonus ? parseFloat(data.bonus) : null,
       };
     }
@@ -605,7 +609,8 @@ export default function ContractForm() {
   const addresses = customer?.addresses || [];
   const bankCards = customer?.bankCards?.filter((c) => c.isActive) || [];
   const documents = customer?.identityDocuments?.filter((d) => d.isActive) || [];
-  const meters = customer?.meters?.filter((m) => m.isActive) || [];
+  const meters = customer?.meters || [];
+  const selectedMeter = meters.find(m => m.id.toString() === selectedMeterId);
   const stressfreiEmails = customer?.stressfreiEmails?.filter((e: { isActive: boolean }) => e.isActive) || [];
   const platforms = platformsData?.data || [];
   const cancellationPeriods = cancellationPeriodsData?.data || [];
@@ -658,7 +663,7 @@ export default function ContractForm() {
   return (
     <div>
       <div className="flex items-center gap-4 mb-6">
-        <Button variant="ghost" size="sm" onClick={() => navigate(backTo || (isEdit ? `/contracts/${id}` : '/contracts'))}>
+        <Button variant="ghost" size="sm" onClick={() => navigate(back.to, { state: back.state })}>
           <ArrowLeft className="w-4 h-4" />
         </Button>
         <h1 className="text-2xl font-bold">
@@ -951,10 +956,10 @@ export default function ContractForm() {
                 label="Zähler"
                 {...register('meterId')}
                 options={meters
-                  .filter((m) => m.type === contractType)
+                  .filter((m) => m.type === contractType && (m.isActive || m.id.toString() === watch('meterId')))
                   .map((m) => ({
                     value: m.id,
-                    label: `${m.meterNumber}${m.location ? ` (${m.location})` : ''}`,
+                    label: `${m.meterNumber}${m.location ? ` (${m.location})` : ''}${!m.isActive ? ' (deaktiviert)' : ''}`,
                   }))}
               />
               <Input
@@ -975,11 +980,19 @@ export default function ContractForm() {
               )}
               <Input label="Grundpreis (€/Monat)" type="number" step="any" {...register('basePrice')} />
               <Input
-                label="Arbeitspreis (€/kWh)"
+                label={selectedMeter?.tariffModel === 'DUAL' ? 'HT-Arbeitspreis (€/kWh)' : 'Arbeitspreis (€/kWh)'}
                 type="number"
                 step="any"
                 {...register('unitPrice')}
               />
+              {selectedMeter?.tariffModel === 'DUAL' && (
+                <Input
+                  label="NT-Arbeitspreis (€/kWh)"
+                  type="number"
+                  step="any"
+                  {...register('unitPriceNt')}
+                />
+              )}
               <Input label="Bonus (€)" type="number" step="0.01" {...register('bonus')} />
             </div>
 
@@ -1409,7 +1422,7 @@ export default function ContractForm() {
         </Card>
 
         <div className="flex justify-end gap-4">
-          <Button type="button" variant="secondary" onClick={() => navigate(backTo || (isEdit ? `/contracts/${id}` : '/contracts'))}>
+          <Button type="button" variant="secondary" onClick={() => navigate(back.to, { state: back.state })}>
             Abbrechen
           </Button>
           <Button type="submit" disabled={isLoading}>

frontend/src/pages/contracts/ContractList.tsx

@@ -1,6 +1,7 @@
 import { useState, useEffect, useMemo } from 'react';
 import { useQuery, useMutation, useQueryClient, useQueries } from '@tanstack/react-query';
 import { Link, useSearchParams, useNavigate } from 'react-router-dom';
+import { pushHistory } from '../../utils/navigation';
 import { contractApi, ContractTreeNode } from '../../services/api';
 import { useAuth } from '../../context/AuthContext';
 import Card from '../../components/ui/Card';
@@ -271,7 +272,7 @@ export default function ContractList() {
                 <div className="w-6" /> // Platzhalter für Ausrichtung
               ) : null}
 
-              <Link to={`/contracts/${contract.id}`} state={{ from: '/contracts' }} className="font-mono flex items-center gap-1 hover:text-blue-600 hover:underline">
+              <Link to={`/contracts/${contract.id}`} state={pushHistory('/contracts')} className="font-mono flex items-center gap-1 hover:text-blue-600 hover:underline">
                 {contract.contractNumber}
                 <CopyButton value={contract.contractNumber} />
               </Link>
@@ -456,7 +457,7 @@ export default function ContractList() {
                     {data.data.map((contract) => (
                       <tr key={contract.id} className="border-b hover:bg-gray-50">
                         <td className="py-3 px-4 font-mono text-sm">
-                          <Link to={`/contracts/${contract.id}`} state={{ from: '/contracts' }} className="text-blue-600 hover:underline">
+                          <Link to={`/contracts/${contract.id}`} state={pushHistory('/contracts')} className="text-blue-600 hover:underline">
                             {contract.contractNumber}
                           </Link>
                         </td>
@@ -465,7 +466,7 @@ export default function ContractList() {
                             {contract.customer && (
                               <Link
                                 to={`/customers/${contract.customer.id}`}
-                                state={{ from: '/contracts' }}
+                                state={pushHistory('/contracts')}
                                 className="text-blue-600 hover:underline"
                               >
                                 {contract.customer.companyName ||
@@ -505,7 +506,7 @@ export default function ContractList() {
                               <Eye className="w-4 h-4" />
                             </Button>
                             {hasPermission('contracts:update') && !isCustomer && (
-                              <Link to={`/contracts/${contract.id}/edit`} state={{ from: '/contracts' }}>
+                              <Link to={`/contracts/${contract.id}/edit`} state={pushHistory('/contracts')}>
                                 <Button variant="ghost" size="sm">
                                   <Edit className="w-4 h-4" />
                                 </Button>

frontend/src/pages/customers/CustomerDetail.tsx

@@ -1,5 +1,6 @@
 import { useState, useEffect } from 'react';
 import { useParams, Link, useNavigate, useSearchParams, useLocation } from 'react-router-dom';
+import { pushHistory, popHistory } from '../../utils/navigation';
 import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
 import { customerApi, addressApi, bankCardApi, documentApi, meterApi, uploadApi, contractApi, stressfreiEmailApi, emailProviderApi, gdprApi, StressfreiEmail, ContractTreeNode } from '../../services/api';
 import { EmailClientTab } from '../../components/email';
@@ -22,7 +23,7 @@ export default function CustomerDetail({ portalCustomerId }: { portalCustomerId?
   const queryClient = useQueryClient();
   const { hasPermission, isCustomerPortal } = useAuth();
   const location = useLocation();
-  const backTo = (location.state as any)?.from as string | undefined;
+  const back = popHistory(location.state, isCustomerPortal ? '/' : '/customers');
   const [searchParams, setSearchParams] = useSearchParams();
   const customerId = portalCustomerId || parseInt(id!);
   const defaultTab = searchParams.get('tab') || 'addresses';
@@ -204,7 +205,7 @@ export default function CustomerDetail({ portalCustomerId }: { portalCustomerId?
     <div>
       <div className="flex items-center justify-between mb-6">
         <div className="flex items-center gap-3">
-          <Button variant="ghost" size="sm" onClick={() => navigate(backTo || (isCustomerPortal ? '/' : '/customers'))}>
+          <Button variant="ghost" size="sm" onClick={() => navigate(back.to, { state: back.state })}>
             <ArrowLeft className="w-4 h-4" />
           </Button>
           <div>
@@ -221,7 +222,7 @@ export default function CustomerDetail({ portalCustomerId }: { portalCustomerId?
         </div>
         <div className="flex gap-2">
           {hasPermission('customers:update') && (
-            <Link to={`/customers/${id}/edit`} state={{ from: `/customers/${id}` }}>
+            <Link to={`/customers/${id}/edit`} state={pushHistory(location.pathname + location.search, (location as any).state)}>
               <Button variant="secondary">
                 <Edit className="w-4 h-4 mr-2" />
                 Bearbeiten
@@ -649,7 +650,7 @@ function AddressesTab({
   const queryClient = useQueryClient();
   const deleteMutation = useMutation({
     mutationFn: addressApi.delete,
-    onSuccess: () => queryClient.invalidateQueries({ queryKey: ['customer', customerId.toString()] }),
+    onSuccess: () => queryClient.invalidateQueries({ queryKey: ['customer', customerId] }),
   });
 
   return (
@@ -746,18 +747,18 @@ function BankCardsTab({
   const updateMutation = useMutation({
     mutationFn: ({ id, data }: { id: number; data: Partial<BankCard> }) =>
       bankCardApi.update(id, data),
-    onSuccess: () => queryClient.invalidateQueries({ queryKey: ['customer', customerId.toString()] }),
+    onSuccess: () => queryClient.invalidateQueries({ queryKey: ['customer', customerId] }),
   });
 
   const deleteMutation = useMutation({
     mutationFn: bankCardApi.delete,
-    onSuccess: () => queryClient.invalidateQueries({ queryKey: ['customer', customerId.toString()] }),
+    onSuccess: () => queryClient.invalidateQueries({ queryKey: ['customer', customerId] }),
   });
 
   const handleDocumentUpload = async (cardId: number, file: File) => {
     try {
       await uploadApi.uploadBankCardDocument(cardId, file);
-      queryClient.invalidateQueries({ queryKey: ['customer', customerId.toString()] });
+      queryClient.invalidateQueries({ queryKey: ['customer', customerId] });
     } catch (error) {
       console.error('Upload fehlgeschlagen:', error);
       alert('Upload fehlgeschlagen');
@@ -768,7 +769,7 @@ function BankCardsTab({
     if (!confirm('Dokument wirklich löschen?')) return;
     try {
       await uploadApi.deleteBankCardDocument(cardId);
-      queryClient.invalidateQueries({ queryKey: ['customer', customerId.toString()] });
+      queryClient.invalidateQueries({ queryKey: ['customer', customerId] });
     } catch (error) {
       console.error('Löschen fehlgeschlagen:', error);
       alert('Löschen fehlgeschlagen');
@@ -972,18 +973,18 @@ function DocumentsTab({
   const updateMutation = useMutation({
     mutationFn: ({ id, data }: { id: number; data: Partial<IdentityDocument> }) =>
       documentApi.update(id, data),
-    onSuccess: () => queryClient.invalidateQueries({ queryKey: ['customer', customerId.toString()] }),
+    onSuccess: () => queryClient.invalidateQueries({ queryKey: ['customer', customerId] }),
   });
 
   const deleteMutation = useMutation({
     mutationFn: documentApi.delete,
-    onSuccess: () => queryClient.invalidateQueries({ queryKey: ['customer', customerId.toString()] }),
+    onSuccess: () => queryClient.invalidateQueries({ queryKey: ['customer', customerId] }),
   });
 
   const handleDocumentUpload = async (docId: number, file: File) => {
     try {
       await uploadApi.uploadIdentityDocument(docId, file);
-      queryClient.invalidateQueries({ queryKey: ['customer', customerId.toString()] });
+      queryClient.invalidateQueries({ queryKey: ['customer', customerId] });
     } catch (error) {
       console.error('Upload fehlgeschlagen:', error);
       alert('Upload fehlgeschlagen');
@@ -994,7 +995,7 @@ function DocumentsTab({
     if (!confirm('Dokument wirklich löschen?')) return;
     try {
       await uploadApi.deleteIdentityDocument(docId);
-      queryClient.invalidateQueries({ queryKey: ['customer', customerId.toString()] });
+      queryClient.invalidateQueries({ queryKey: ['customer', customerId] });
     } catch (error) {
       console.error('Löschen fehlgeschlagen:', error);
       alert('Löschen fehlgeschlagen');
@@ -1204,26 +1205,34 @@ function MetersTab({
   onAdd: () => void;
   onEdit: (meter: Meter) => void;
 }) {
-  const [showReadingModal, setShowReadingModal] = useState<{ meterId: number; meterType: 'ELECTRICITY' | 'GAS' } | null>(null);
+  const [showReadingModal, setShowReadingModal] = useState<{ meterId: number; meterType: 'ELECTRICITY' | 'GAS'; tariffModel?: string } | null>(null);
   const [expandedMeter, setExpandedMeter] = useState<number | null>(null);
-  const [editingReading, setEditingReading] = useState<{ meterId: number; meterType: 'ELECTRICITY' | 'GAS'; reading: any } | null>(null);
+  const [editingReading, setEditingReading] = useState<{ meterId: number; meterType: 'ELECTRICITY' | 'GAS'; tariffModel?: string; reading: any } | null>(null);
   const queryClient = useQueryClient();
 
   const updateMutation = useMutation({
     mutationFn: ({ id, data }: { id: number; data: Partial<Meter> }) =>
       meterApi.update(id, data),
-    onSuccess: () => queryClient.invalidateQueries({ queryKey: ['customer', customerId.toString()] }),
+    onSuccess: () => queryClient.invalidateQueries({ queryKey: ['customer', customerId] }),
   });
 
+  const [deleteError, setDeleteError] = useState<string | null>(null);
+
   const deleteMutation = useMutation({
     mutationFn: meterApi.delete,
-    onSuccess: () => queryClient.invalidateQueries({ queryKey: ['customer', customerId.toString()] }),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['customer', customerId] });
+      setDeleteError(null);
+    },
+    onError: (err) => {
+      setDeleteError(err instanceof Error ? err.message : 'Fehler beim Löschen');
+    },
   });
 
   const deleteReadingMutation = useMutation({
     mutationFn: ({ meterId, readingId }: { meterId: number; readingId: number }) =>
       meterApi.deleteReading(meterId, readingId),
-    onSuccess: () => queryClient.invalidateQueries({ queryKey: ['customer', customerId.toString()] }),
+    onSuccess: () => queryClient.invalidateQueries({ queryKey: ['customer', customerId] }),
   });
 
   const filtered = showInactive ? meters : meters.filter((m) => m.isActive);
@@ -1273,6 +1282,9 @@ function MetersTab({
                     <Badge variant={meter.type === 'ELECTRICITY' ? 'warning' : 'info'}>
                       {meter.type === 'ELECTRICITY' ? 'Strom' : 'Gas'}
                     </Badge>
+                    {meter.tariffModel === 'DUAL' && (
+                      <Badge variant="default">HT/NT</Badge>
+                    )}
                     {!meter.isActive && <Badge variant="danger">Inaktiv</Badge>}
                   </div>
                   {canEdit && (
@@ -1281,7 +1293,7 @@ function MetersTab({
                         <Button
                           variant="ghost"
                           size="sm"
-                          onClick={() => setShowReadingModal({ meterId: meter.id, meterType: meter.type })}
+                          onClick={() => setShowReadingModal({ meterId: meter.id, meterType: meter.type, tariffModel: meter.tariffModel })}
                           title="Zählerstand hinzufügen"
                         >
                           <Plus className="w-4 h-4" />
@@ -1371,14 +1383,17 @@ function MetersTab({
                           </span>
                           <div className="flex items-center gap-2">
                             <span className="font-mono flex items-center gap-1">
-                              {reading.value.toLocaleString('de-DE')} {reading.unit}
+                              {reading.valueNt !== undefined && reading.valueNt !== null ? (
-                              <CopyButton value={reading.value.toString()} title="Nur Wert kopieren" />
+                                <>HT: {reading.value.toLocaleString('de-DE')} / NT: {reading.valueNt.toLocaleString('de-DE')} {reading.unit}</>
-                              <CopyButton value={`${reading.value.toLocaleString('de-DE')} ${reading.unit}`} title="Mit Einheit kopieren" />
+                              ) : (
+                                <>{reading.value.toLocaleString('de-DE')} {reading.unit}</>
+                              )}
+                              <CopyButton value={reading.value.toString()} title="Wert kopieren" />
                             </span>
                             {canEdit && (
                               <div className="opacity-0 group-hover:opacity-100 flex gap-1">
                                 <button
-                                  onClick={() => setEditingReading({ meterId: meter.id, meterType: meter.type, reading })}
+                                  onClick={() => setEditingReading({ meterId: meter.id, meterType: meter.type, tariffModel: meter.tariffModel, reading })}
                                   className="text-gray-400 hover:text-blue-600"
                                   title="Bearbeiten"
                                 >
@@ -1417,6 +1432,7 @@ function MetersTab({
           onClose={() => setShowReadingModal(null)}
           meterId={showReadingModal.meterId}
           meterType={showReadingModal.meterType}
+          tariffModel={showReadingModal.tariffModel as any}
           customerId={customerId}
         />
       )}
@@ -1427,10 +1443,43 @@ function MetersTab({
           onClose={() => setEditingReading(null)}
           meterId={editingReading.meterId}
           meterType={editingReading.meterType}
+          tariffModel={editingReading.tariffModel as any}
           customerId={customerId}
           reading={editingReading.reading}
         />
       )}
+
+      {/* Fehler-Modal beim Löschen (z.B. Zähler noch an Vertrag) */}
+      {deleteError && (
+        <Modal isOpen={true} onClose={() => setDeleteError(null)} title="Zähler kann nicht gelöscht werden">
+          <p className="text-sm text-gray-600 mb-4">
+            Der Zähler ist noch folgenden Verträgen zugeordnet und kann daher nicht gelöscht werden:
+          </p>
+          <div className="space-y-2">
+            {deleteError.match(/[A-Z]+-[A-Z0-9]+/g)?.map((contractNumber) => (
+              <Link
+                key={contractNumber}
+                to={`/contracts?search=${contractNumber}`}
+                onClick={() => setDeleteError(null)}
+                className="flex items-center gap-2 p-3 bg-gray-50 border rounded-lg text-blue-600 hover:bg-blue-50 hover:border-blue-300 transition-colors"
+              >
+                <FileText className="w-4 h-4" />
+                <span className="font-mono">{contractNumber}</span>
+              </Link>
+            )) ?? (
+              <p className="text-sm text-red-600">{deleteError}</p>
+            )}
+          </div>
+          <p className="text-xs text-gray-500 mt-4">
+            Bitte entfernen Sie den Zähler zuerst aus den oben genannten Verträgen.
+          </p>
+          <div className="flex justify-end mt-4">
+            <Button variant="secondary" onClick={() => setDeleteError(null)}>
+              Schließen
+            </Button>
+          </div>
+        </Modal>
+      )}
     </div>
   );
 }
@@ -1457,7 +1506,7 @@ function ContractsTab({
   const deleteMutation = useMutation({
     mutationFn: contractApi.delete,
     onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['customer', customerId.toString()] });
+      queryClient.invalidateQueries({ queryKey: ['customer', customerId] });
       queryClient.invalidateQueries({ queryKey: ['customers'] });
       queryClient.invalidateQueries({ queryKey: ['contracts'] });
       queryClient.invalidateQueries({ queryKey: ['contract-tree', customerId] });
@@ -1549,7 +1598,7 @@ function ContractsTab({
                 <div className="w-6" /> // Platzhalter für Ausrichtung
               ) : null}
 
-              <Link to={`/contracts/${contract.id}`} state={{ from: `/customers/${customerId}?tab=contracts` }} className="font-mono flex items-center gap-1 text-blue-600 hover:underline">
+              <Link to={`/contracts/${contract.id}`} state={pushHistory(location.pathname + location.search, (location as any).state)} className="font-mono flex items-center gap-1 text-blue-600 hover:underline">
                 {contract.contractNumber}
                 <CopyButton value={contract.contractNumber} />
               </Link>
@@ -2054,7 +2103,7 @@ function AddressModal({
   const createMutation = useMutation({
     mutationFn: (data: typeof formData) => addressApi.create(customerId, data),
     onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['customer', customerId.toString()] });
+      queryClient.invalidateQueries({ queryKey: ['customer', customerId] });
       onClose();
       setFormData({
         type: 'DELIVERY_RESIDENCE',
@@ -2071,7 +2120,7 @@ function AddressModal({
   const updateMutation = useMutation({
     mutationFn: (data: typeof formData) => addressApi.update(address!.id, data),
     onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['customer', customerId.toString()] });
+      queryClient.invalidateQueries({ queryKey: ['customer', customerId] });
       onClose();
     },
   });
@@ -2201,7 +2250,7 @@ function BankCardModal({
   const createMutation = useMutation({
     mutationFn: (data: any) => bankCardApi.create(customerId, data),
     onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['customer', customerId.toString()] });
+      queryClient.invalidateQueries({ queryKey: ['customer', customerId] });
       onClose();
       setFormData({ accountHolder: '', iban: '', bic: '', bankName: '', expiryDate: '', isActive: true });
     },
@@ -2210,7 +2259,7 @@ function BankCardModal({
   const updateMutation = useMutation({
     mutationFn: (data: any) => bankCardApi.update(bankCard!.id, data),
     onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['customer', customerId.toString()] });
+      queryClient.invalidateQueries({ queryKey: ['customer', customerId] });
       onClose();
     },
   });
@@ -2333,7 +2382,7 @@ function DocumentModal({
   const createMutation = useMutation({
     mutationFn: (data: any) => documentApi.create(customerId, data),
     onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['customer', customerId.toString()] });
+      queryClient.invalidateQueries({ queryKey: ['customer', customerId] });
       onClose();
       setFormData({
         type: 'ID_CARD',
@@ -2351,7 +2400,7 @@ function DocumentModal({
   const updateMutation = useMutation({
     mutationFn: (data: any) => documentApi.update(document!.id, data),
     onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['customer', customerId.toString()] });
+      queryClient.invalidateQueries({ queryKey: ['customer', customerId] });
       onClose();
     },
   });
@@ -2498,6 +2547,7 @@ function MeterModal({
   const getInitialFormData = () => ({
     meterNumber: meter?.meterNumber || '',
     type: meter?.type || 'ELECTRICITY' as const,
+    tariffModel: meter?.tariffModel || 'SINGLE' as const,
     location: meter?.location || '',
     isActive: meter?.isActive ?? true,
   });
@@ -2507,16 +2557,16 @@ function MeterModal({
   const createMutation = useMutation({
     mutationFn: (data: any) => meterApi.create(customerId, data),
     onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['customer', customerId.toString()] });
+      queryClient.invalidateQueries({ queryKey: ['customer', customerId] });
       onClose();
-      setFormData({ meterNumber: '', type: 'ELECTRICITY', location: '', isActive: true });
+      setFormData({ meterNumber: '', type: 'ELECTRICITY', tariffModel: 'SINGLE', location: '', isActive: true });
     },
   });
 
   const updateMutation = useMutation({
     mutationFn: (data: any) => meterApi.update(meter!.id, data),
     onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['customer', customerId.toString()] });
+      queryClient.invalidateQueries({ queryKey: ['customer', customerId] });
       onClose();
     },
   });
@@ -2557,6 +2607,18 @@ function MeterModal({
           ]}
         />
 
+        {formData.type === 'ELECTRICITY' && (
+          <Select
+            label="Tarifmodell"
+            value={formData.tariffModel}
+            onChange={(e) => setFormData({ ...formData, tariffModel: e.target.value as any })}
+            options={[
+              { value: 'SINGLE', label: 'Eintarifzähler (Standard)' },
+              { value: 'DUAL', label: 'Zweitarifzähler (HT/NT)' },
+            ]}
+          />
+        )}
+
         <Input
           label="Standort"
           value={formData.location}
@@ -2594,6 +2656,7 @@ function MeterReadingModal({
   onClose,
   meterId,
   meterType,
+  tariffModel,
   customerId,
   reading,
 }: {
@@ -2601,47 +2664,63 @@ function MeterReadingModal({
   onClose: () => void;
   meterId: number;
   meterType: 'ELECTRICITY' | 'GAS';
+  tariffModel?: 'SINGLE' | 'DUAL';
   customerId: number;
-  reading?: { id: number; readingDate: string; value: number; unit: string; notes?: string } | null;
+  reading?: { id: number; readingDate: string; value: number; valueNt?: number; unit: string; notes?: string } | null;
 }) {
   const queryClient = useQueryClient();
   const isEditing = !!reading;
   const defaultUnit = meterType === 'ELECTRICITY' ? 'kWh' : 'm³';
+  const isDualTariff = tariffModel === 'DUAL';
 
   const getInitialFormData = () => ({
     readingDate: reading?.readingDate
       ? new Date(reading.readingDate).toISOString().split('T')[0]
       : new Date().toISOString().split('T')[0],
     value: reading?.value?.toString() || '',
+    valueNt: reading?.valueNt?.toString() || '',
     notes: reading?.notes || '',
   });
 
   const [formData, setFormData] = useState(getInitialFormData);
 
+  const [error, setError] = useState<string | null>(null);
+
   const createMutation = useMutation({
     mutationFn: (data: any) => meterApi.addReading(meterId, data),
     onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['customer', customerId.toString()] });
+      queryClient.invalidateQueries({ queryKey: ['customer', customerId] });
+      setError(null);
       onClose();
     },
+    onError: (err) => {
+      setError(err instanceof Error ? err.message : 'Fehler beim Speichern');
+    },
   });
 
   const updateMutation = useMutation({
     mutationFn: (data: any) => meterApi.updateReading(meterId, reading!.id, data),
     onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['customer', customerId.toString()] });
+      queryClient.invalidateQueries({ queryKey: ['customer', customerId] });
+      setError(null);
       onClose();
     },
+    onError: (err) => {
+      setError(err instanceof Error ? err.message : 'Fehler beim Speichern');
+    },
   });
 
   const handleSubmit = (e: React.FormEvent) => {
     e.preventDefault();
-    const data = {
+    const data: Record<string, unknown> = {
       readingDate: new Date(formData.readingDate),
       value: parseFloat(formData.value),
       unit: defaultUnit,
       notes: formData.notes || undefined,
     };
+    if (isDualTariff && formData.valueNt) {
+      data.valueNt = parseFloat(formData.valueNt);
+    }
     if (isEditing) {
       updateMutation.mutate(data);
     } else {
@@ -2667,10 +2746,10 @@ function MeterReadingModal({
           required
         />
 
-        <div className="grid grid-cols-3 gap-4">
+        <div className={`grid ${isDualTariff ? 'grid-cols-2' : 'grid-cols-3'} gap-4`}>
-          <div className="col-span-2">
+          <div className={isDualTariff ? '' : 'col-span-2'}>
             <Input
-              label="Zählerstand"
+              label={isDualTariff ? 'HT-Stand (Hochtarif)' : 'Zählerstand'}
               type="number"
               step="0.01"
               value={formData.value}
@@ -2678,12 +2757,26 @@ function MeterReadingModal({
               required
             />
           </div>
-          <div>
+          {isDualTariff && (
-            <label className="block text-sm font-medium text-gray-700 mb-1">Einheit</label>
+            <div>
-            <div className="h-10 flex items-center px-3 bg-gray-100 border border-gray-300 rounded-md text-gray-700">
+              <Input
-              {defaultUnit}
+                label="NT-Stand (Niedertarif)"
+                type="number"
+                step="0.01"
+                value={formData.valueNt}
+                onChange={(e) => setFormData({ ...formData, valueNt: e.target.value })}
+                required
+              />
             </div>
-          </div>
+          )}
+          {!isDualTariff && (
+            <div>
+              <label className="block text-sm font-medium text-gray-700 mb-1">Einheit</label>
+              <div className="h-10 flex items-center px-3 bg-gray-100 border border-gray-300 rounded-md text-gray-700">
+                {defaultUnit}
+              </div>
+            </div>
+          )}
         </div>
 
         <Input
@@ -2693,6 +2786,12 @@ function MeterReadingModal({
           placeholder="Optionale Notizen..."
         />
 
+        {error && (
+          <div className="p-3 bg-red-50 border border-red-200 rounded-lg text-sm text-red-700">
+            {error}
+          </div>
+        )}
+
         <div className="flex justify-end gap-2">
           <Button type="button" variant="secondary" onClick={onClose}>
             Abbrechen
@@ -2732,12 +2831,12 @@ function StressfreiEmailsTab({
   const updateMutation = useMutation({
     mutationFn: ({ id, data }: { id: number; data: Partial<StressfreiEmail> }) =>
       stressfreiEmailApi.update(id, data),
-    onSuccess: () => queryClient.invalidateQueries({ queryKey: ['customer', customerId.toString()] }),
+    onSuccess: () => queryClient.invalidateQueries({ queryKey: ['customer', customerId] }),
   });
 
   const deleteMutation = useMutation({
     mutationFn: stressfreiEmailApi.delete,
-    onSuccess: () => queryClient.invalidateQueries({ queryKey: ['customer', customerId.toString()] }),
+    onSuccess: () => queryClient.invalidateQueries({ queryKey: ['customer', customerId] }),
   });
 
   const filtered = showInactive ? emails : emails.filter((e) => e.isActive);
@@ -3087,7 +3186,7 @@ function StressfreiEmailModal({
       const result = await stressfreiEmailApi.enableMailbox(email.id);
       if (result.success) {
         setMailboxEnabled(true);
-        queryClient.invalidateQueries({ queryKey: ['customer', customerId.toString()] });
+        queryClient.invalidateQueries({ queryKey: ['customer', customerId] });
         queryClient.invalidateQueries({ queryKey: ['mailbox-accounts', customerId] });
       } else {
         setProvisionError(result.error || 'Mailbox-Aktivierung fehlgeschlagen');
@@ -3108,7 +3207,7 @@ function StressfreiEmailModal({
         setMailboxEnabled(result.data.hasMailbox);
         if (result.data.wasUpdated) {
           // DB wurde aktualisiert, Query invalidieren
-          queryClient.invalidateQueries({ queryKey: ['customer', customerId.toString()] });
+          queryClient.invalidateQueries({ queryKey: ['customer', customerId] });
         }
       }
     } catch (error) {
@@ -3199,7 +3298,7 @@ function StressfreiEmailModal({
       });
     },
     onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['customer', customerId.toString()] });
+      queryClient.invalidateQueries({ queryKey: ['customer', customerId] });
       queryClient.invalidateQueries({ queryKey: ['mailbox-accounts', customerId] });
       setLocalPart('');
       setNotes('');
@@ -3216,7 +3315,7 @@ function StressfreiEmailModal({
     mutationFn: (data: Partial<StressfreiEmail>) =>
       stressfreiEmailApi.update(email!.id, data),
     onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['customer', customerId.toString()] });
+      queryClient.invalidateQueries({ queryKey: ['customer', customerId] });
       onClose();
     },
   });
@@ -3664,6 +3763,7 @@ function ConsentTab({
     try {
       await uploadApi.uploadPrivacyPolicy(customerId, file);
       onUpdate?.();
+      queryClient.invalidateQueries({ queryKey: ['customer-consents', customerId] });
     } catch (error) {
       console.error('Upload fehlgeschlagen:', error);
       alert('Upload fehlgeschlagen');
@@ -3675,6 +3775,7 @@ function ConsentTab({
     try {
       await uploadApi.deletePrivacyPolicy(customerId);
       onUpdate?.();
+      queryClient.invalidateQueries({ queryKey: ['customer-consents', customerId] });
     } catch (error) {
       console.error('Löschen fehlgeschlagen:', error);
       alert('Löschen fehlgeschlagen');

frontend/src/pages/customers/CustomerForm.tsx

@@ -1,5 +1,6 @@
 import { useEffect } from 'react';
 import { useNavigate, useParams, useLocation } from 'react-router-dom';
+import { popHistory } from '../../utils/navigation';
 import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
 import { useForm } from 'react-hook-form';
 import { customerApi } from '../../services/api';
@@ -17,7 +18,7 @@ export default function CustomerForm() {
   const location = useLocation();
   const queryClient = useQueryClient();
   const isEdit = !!id;
-  const backTo = (location.state as any)?.from as string | undefined;
+  const back = popHistory(location.state, isEdit ? `/customers/${id}` : '/customers');
 
   const { register, handleSubmit, reset, watch, setValue, formState: { errors } } = useForm<CustomerFormData>();
   const customerType = watch('type');
@@ -234,7 +235,7 @@ export default function CustomerForm() {
         </Card>
 
         <div className="flex justify-end gap-4">
-          <Button type="button" variant="secondary" onClick={() => navigate(backTo || (isEdit ? `/customers/${id}` : '/customers'))}>
+          <Button type="button" variant="secondary" onClick={() => navigate(back.to, { state: back.state })}>
             Abbrechen
           </Button>
           <Button type="submit" disabled={isLoading}>

frontend/src/pages/customers/CustomerList.tsx

@@ -1,6 +1,7 @@
 import { useState } from 'react';
 import { useQuery } from '@tanstack/react-query';
 import { Link } from 'react-router-dom';
+import { pushHistory } from '../../utils/navigation';
 import { customerApi } from '../../services/api';
 import { useAuth } from '../../context/AuthContext';
 import Card from '../../components/ui/Card';
@@ -78,12 +79,12 @@ export default function CustomerList() {
                   {data.data.map((customer) => (
                     <tr key={customer.id} className="border-b hover:bg-gray-50">
                       <td className="py-3 px-4 font-mono text-sm">
-                        <Link to={`/customers/${customer.id}`} state={{ from: '/customers' }} className="text-blue-600 hover:underline">
+                        <Link to={`/customers/${customer.id}`} state={pushHistory('/customers')} className="text-blue-600 hover:underline">
                           {customer.customerNumber}
                         </Link>
                       </td>
                       <td className="py-3 px-4">
-                        <Link to={`/customers/${customer.id}`} state={{ from: '/customers' }} className="text-blue-600 hover:underline">
+                        <Link to={`/customers/${customer.id}`} state={pushHistory('/customers')} className="text-blue-600 hover:underline">
                           {customer.type === 'BUSINESS' && customer.companyName
                             ? customer.companyName
                             : `${customer.firstName} ${customer.lastName}`}

frontend/src/pages/settings/AuditLogs.tsx

@@ -36,10 +36,15 @@ const RESOURCE_OPTIONS = [
   { value: 'Contract', label: 'Verträge' },
   { value: 'User', label: 'Benutzer' },
   { value: 'BankCard', label: 'Bankdaten' },
-  { value: 'IdentityDocument', label: 'Ausweisdokumente' },
+  { value: 'IdentityDocument', label: 'Ausweise' },
-  { value: 'Authentication', label: 'Authentifizierung' },
+  { value: 'Address', label: 'Adressen' },
+  { value: 'Meter', label: 'Zähler' },
+  { value: 'ContractTask', label: 'Aufgaben' },
+  { value: 'Authentication', label: 'Anmeldung' },
   { value: 'CustomerConsent', label: 'Einwilligungen' },
-  { value: 'GDPR', label: 'DSGVO' },
+  { value: 'GDPR', label: 'DSGVO / Vollmacht' },
+  { value: 'EmailProviderConfig', label: 'E-Mail-Provider' },
+  { value: 'AppSetting', label: 'Einstellungen' },
 ];
 
 function formatDate(date: string): string {
@@ -354,11 +359,12 @@ export default function AuditLogs() {
                         </span>
                       </td>
                       <td className="py-3 px-4">
-                        <div>{log.resourceType}</div>
+                        {log.resourceLabel ? (
-                        {log.resourceLabel && (
+                          <div className="text-sm truncate max-w-[300px]" title={log.resourceLabel}>
-                          <div className="text-xs text-gray-500 truncate max-w-[200px]" title={log.resourceLabel}>
                             {log.resourceLabel}
                           </div>
+                        ) : (
+                          <div className="text-sm text-gray-500">{log.resourceType}</div>
                         )}
                       </td>
                       <td className="py-3 px-4 font-mono text-xs">{log.ipAddress}</td>

frontend/src/services/api.ts

@@ -655,6 +655,15 @@ export const contractApi = {
     const res = await api.get<ApiResponse<import('../types').CockpitResult>>('/contracts/cockpit');
     return res.data;
   },
+  // Folgezähler
+  addSuccessorMeter: async (contractId: number, data: { meterId: number; installedAt?: string; finalReadingPrevious?: number }) => {
+    const res = await api.post<ApiResponse<any>>(`/contracts/${contractId}/successor-meter`, data);
+    return res.data;
+  },
+  removeContractMeter: async (contractId: number, contractMeterId: number) => {
+    const res = await api.delete<ApiResponse<void>>(`/contracts/${contractId}/contract-meter/${contractMeterId}`);
+    return res.data;
+  },
   // Snooze: Vertrag zurückstellen
   snooze: async (id: number, data: { nextReviewDate?: string; months?: number }) => {
     const res = await api.patch<ApiResponse<{ id: number; contractNumber: string; nextReviewDate: string | null }>>(`/contracts/${id}/snooze`, data);

frontend/src/types/index.ts

@@ -152,16 +152,30 @@ export interface IdentityDocument {
   licenseIssueDate?: string;
 }
 
+export type MeterTariffModel = 'SINGLE' | 'DUAL';
+
 export interface Meter {
   id: number;
   customerId: number;
   meterNumber: string;
   type: 'ELECTRICITY' | 'GAS';
+  tariffModel: MeterTariffModel;
   location?: string;
   isActive: boolean;
   readings?: MeterReading[];
 }
 
+export interface ContractMeter {
+  id: number;
+  energyContractDetailsId: number;
+  meterId: number;
+  meter?: Meter;
+  position: number;
+  installedAt?: string;
+  removedAt?: string;
+  finalReading?: number;
+}
+
 export type MeterReadingStatus = 'RECORDED' | 'REPORTED' | 'TRANSFERRED';
 
 export interface MeterReading {
@@ -169,6 +183,7 @@ export interface MeterReading {
   meterId: number;
   readingDate: string;
   value: number;
+  valueNt?: number;     // NT-Wert (nur bei Zweitarifzähler)
   unit: string;
   notes?: string;
   reportedBy?: string;
@@ -396,11 +411,13 @@ export interface EnergyContractDetails {
   annualConsumption?: number;      // kWh für Strom, m³ für Gas
   annualConsumptionKwh?: number;   // kWh für Gas (zusätzlich zu m³)
   basePrice?: number;              // €/Monat
-  unitPrice?: number;              // €/kWh (Arbeitspreis)
+  unitPrice?: number;              // €/kWh (Arbeitspreis) - bei HT/NT: HT-Preis
+  unitPriceNt?: number;            // €/kWh NT-Preis (nur bei Zweitarifzähler)
   bonus?: number;
   previousProviderName?: string;
   previousCustomerNumber?: string;
   invoices?: Invoice[];            // Rechnungen
+  contractMeters?: ContractMeter[];  // Zähler-Zuordnungen (inkl. Folgezähler)
 }
 
 export interface InternetContractDetails {
@@ -575,6 +592,7 @@ export interface ReportedMeterReading {
   createdAt: string;
   meter: { id: number; meterNumber: string; type: string };
   customer: { id: number; customerNumber: string; name: string };
+  contract?: { id: number; contractNumber: string };
   providerPortal?: {
     providerName: string;
     portalUrl: string;

frontend/src/utils/energyCalculations.ts

@@ -1,4 +1,4 @@
-import type { MeterReading } from '../types';
+import type { MeterReading, ContractMeter } from '../types';
 
 // Konstante für Gas → kWh Umrechnung (Standard Erdgas H)
 export const GAS_TO_KWH_FACTOR = 10.5;
@@ -8,6 +8,8 @@ export interface ConsumptionCalculation {
   type: 'exact' | 'projected' | 'insufficient' | 'none';
   consumptionM3?: number;      // Nur bei Gas
   consumptionKwh: number;
+  consumptionHt?: number;      // Nur bei HT/NT: HT-Verbrauch in kWh
+  consumptionNt?: number;      // Nur bei HT/NT: NT-Verbrauch in kWh
   startReading?: MeterReading;
   endReading?: MeterReading;
   projectedEndDate?: string;   // Nur bei Hochrechnung
@@ -17,7 +19,8 @@ export interface ConsumptionCalculation {
 // Ergebnis der Kostenberechnung
 export interface CostCalculation {
   annualBaseCost: number;        // basePrice × 12
-  annualConsumptionCost: number; // verbrauch × unitPrice
+  annualConsumptionCost: number; // verbrauch × unitPrice (HT bei Zweitarif)
+  annualConsumptionCostNt?: number; // NT-Verbrauch × unitPriceNt
   annualTotalCost: number;       // Summe
   monthlyPayment: number;        // annualTotalCost / 12
   bonus?: number;
@@ -94,7 +97,6 @@ export function calculateConsumption(
     (a, b) => new Date(a.readingDate).getTime() - new Date(b.readingDate).getTime()
   );
 
-  const firstReading = sorted[0];
   const lastReading = sorted[sorted.length - 1];
 
   // Prüfen ob Endzählerstand am/nach Vertragsende liegt
@@ -103,16 +105,39 @@ export function calculateConsumption(
   lastReadingDate.setHours(0, 0, 0, 0);
   contractEndDate.setHours(0, 0, 0, 0);
 
-  // Fall A: Exakter Verbrauch (Endzählerstand am oder nach Vertragsende)
+  // Verbrauch zwischen aufeinanderfolgenden Ständen berechnen
+  // (Erkennt Zählerwechsel: wenn ein Wert sinkt, wird ab dem neuen Stand weitergerechnet)
+  let totalConsumption = 0;
+  let totalConsumptionNt = 0;
+  const hasNt = sorted.some(r => r.valueNt !== undefined && r.valueNt !== null);
+  let effectiveFirstReading = sorted[0];
+  for (let i = 1; i < sorted.length; i++) {
+    const diff = sorted[i].value - sorted[i - 1].value;
+    if (diff < 0) {
+      totalConsumption = 0;
+      totalConsumptionNt = 0;
+      effectiveFirstReading = sorted[i];
+    } else {
+      totalConsumption += diff;
+      if (hasNt && sorted[i].valueNt != null && sorted[i - 1].valueNt != null) {
+        const diffNt = sorted[i].valueNt! - sorted[i - 1].valueNt!;
+        if (diffNt >= 0) totalConsumptionNt += diffNt;
+      }
+    }
+  }
+
+  const effectiveLastReading = sorted[sorted.length - 1];
+
+  // Fall A: Exakter Verbrauch
   if (lastReadingDate >= contractEndDate) {
-    const consumption = lastReading.value - firstReading.value;
+    const result = formatConsumptionResult('exact', totalConsumption, contractType, effectiveFirstReading, effectiveLastReading);
-    return formatConsumptionResult('exact', consumption, contractType, firstReading, lastReading);
+    if (hasNt) { result.consumptionHt = totalConsumption; result.consumptionNt = totalConsumptionNt; }
+    return result;
   }
 
   // Fall B: Hochrechnung erforderlich
-  const daysBetweenReadings = daysDiff(firstReading.readingDate, lastReading.readingDate);
+  const daysBetweenReadings = daysDiff(effectiveFirstReading.readingDate, effectiveLastReading.readingDate);
 
-  // Mindestens 1 Tag zwischen den Messungen für sinnvolle Hochrechnung
   if (daysBetweenReadings < 1) {
     return {
       type: 'insufficient',
@@ -122,17 +147,26 @@ export function calculateConsumption(
   }
 
   const totalContractDays = daysDiff(startDate, endDate);
-  const measuredConsumption = lastReading.value - firstReading.value;
+  const projectedConsumption = (totalConsumption / daysBetweenReadings) * totalContractDays;
-  const projectedConsumption = (measuredConsumption / daysBetweenReadings) * totalContractDays;
 
-  return formatConsumptionResult(
+  const result = formatConsumptionResult(
     'projected',
     projectedConsumption,
     contractType,
-    firstReading,
+    effectiveFirstReading,
-    lastReading,
+    effectiveLastReading,
     endDate
   );
+
+  if (hasNt) {
+    const projectedNt = (totalConsumptionNt / daysBetweenReadings) * totalContractDays;
+    result.consumptionHt = projectedConsumption;
+    result.consumptionNt = projectedNt;
+    // Gesamt-kWh = HT + NT
+    result.consumptionKwh = projectedConsumption + projectedNt;
+  }
+
+  return result;
 }
 
 /**
@@ -173,7 +207,9 @@ export function calculateCosts(
   consumptionKwh: number,
   basePrice?: number,
   unitPrice?: number,
-  bonus?: number
+  bonus?: number,
+  consumptionNtKwh?: number,
+  unitPriceNt?: number
 ): CostCalculation | null {
   // Mindestens ein Preis muss vorhanden sein
   if (basePrice == null && unitPrice == null) {
@@ -181,17 +217,78 @@ export function calculateCosts(
   }
 
   const annualBaseCost = (basePrice ?? 0) * 12;
+  // Bei HT/NT: consumptionKwh ist nur HT, NT wird separat berechnet
   const annualConsumptionCost = consumptionKwh * (unitPrice ?? 0);
-  const annualTotalCost = annualBaseCost + annualConsumptionCost;
+  const annualConsumptionCostNt = (consumptionNtKwh ?? 0) * (unitPriceNt ?? 0);
+  const annualTotalCost = annualBaseCost + annualConsumptionCost + annualConsumptionCostNt;
   const effectiveAnnualCost = annualTotalCost - (bonus ?? 0);
   const monthlyPayment = effectiveAnnualCost / 12;
 
   return {
     annualBaseCost,
     annualConsumptionCost,
+    annualConsumptionCostNt: annualConsumptionCostNt > 0 ? annualConsumptionCostNt : undefined,
     annualTotalCost,
     monthlyPayment,
     bonus: bonus ?? undefined,
     effectiveAnnualCost,
   };
 }
+
+/**
+ * Berechnet den Verbrauch über mehrere Zähler (Folgezähler).
+ * Pro Zähler wird der Verbrauch einzeln berechnet und dann summiert.
+ */
+export function calculateMultiMeterConsumption(
+  contractMeters: ContractMeter[],
+  startDate: string,
+  endDate: string,
+  contractType: 'ELECTRICITY' | 'GAS'
+): ConsumptionCalculation {
+  if (contractMeters.length === 0) {
+    return { type: 'none', consumptionKwh: 0 };
+  }
+
+  let totalConsumption = 0;
+  let totalConsumptionM3 = 0;
+  let hasExact = true;
+  let hasAny = false;
+  let firstStart: MeterReading | undefined;
+  let lastEnd: MeterReading | undefined;
+
+  for (const cm of contractMeters) {
+    const readings = cm.meter?.readings || [];
+    if (readings.length === 0) continue;
+
+    // Zeitraum für diesen Zähler bestimmen
+    const meterStart = cm.installedAt || startDate;
+    const meterEnd = cm.removedAt || endDate;
+
+    const result = calculateConsumption(readings, meterStart, meterEnd, contractType);
+
+    if (result.type === 'none' || result.type === 'insufficient') continue;
+
+    hasAny = true;
+    if (result.type === 'projected') hasExact = false;
+
+    totalConsumption += result.consumptionKwh;
+    if (result.consumptionM3) totalConsumptionM3 += result.consumptionM3;
+
+    if (!firstStart && result.startReading) firstStart = result.startReading;
+    if (result.endReading) lastEnd = result.endReading;
+  }
+
+  if (!hasAny) {
+    // Fallback: Einzelzähler-Berechnung mit allen Readings
+    const allReadings = contractMeters.flatMap(cm => cm.meter?.readings || []);
+    return calculateConsumption(allReadings, startDate, endDate, contractType);
+  }
+
+  return {
+    type: hasExact ? 'exact' : 'projected',
+    consumptionKwh: totalConsumption,
+    consumptionM3: contractType === 'GAS' ? totalConsumptionM3 : undefined,
+    startReading: firstStart,
+    endReading: lastEnd,
+  };
+}

frontend/src/utils/navigation.ts

@@ -0,0 +1,26 @@
+/**
+ * Navigation-History über location.state.
+ * Jeder Link fügt die aktuelle URL zum Stack hinzu.
+ * Der Zurück-Button poppt den letzten Eintrag und gibt den Rest weiter.
+ */
+
+export interface NavState {
+  history?: string[];
+}
+
+/**
+ * Erstellt den state für einen Link - fügt die aktuelle URL zum History-Stack hinzu.
+ */
+export function pushHistory(currentPath: string, locationState?: unknown): NavState {
+  const prev = (locationState as NavState)?.history || [];
+  return { history: [...prev, currentPath] };
+}
+
+/**
+ * Gibt die Zurück-URL und den verbleibenden History-Stack zurück.
+ */
+export function popHistory(locationState?: unknown, fallback?: string): { to: string; state: NavState } {
+  const history = [...((locationState as NavState)?.history || [])];
+  const to = history.pop() || fallback || '/';
+  return { to, state: { history } };
+}