added new view in contracts customer and contracts

frontend/src/pages/contracts/ContractForm.tsx

@@ -35,6 +35,7 @@ export default function ContractForm() {
       customerId: preselectedCustomerId || '',
       type: 'ELECTRICITY',
       status: 'DRAFT',
+      previousContractId: '',
     },
   });
 
@@ -61,6 +62,13 @@ export default function ContractForm() {
     enabled: !!customerId,
   });
 
+  // Fetch contracts for same customer (for predecessor selection)
+  const { data: customerContractsData } = useQuery({
+    queryKey: ['customer-contracts-for-predecessor', customerId],
+    queryFn: () => contractApi.getAll({ customerId: parseInt(customerId), limit: 1000 }),
+    enabled: !!customerId,
+  });
+
   // Fetch platforms
   const { data: platformsData } = useQuery({
     queryKey: ['platforms'],
@@ -256,6 +264,8 @@ export default function ContractForm() {
         cancellationConfirmationDate: c.cancellationConfirmationDate ? c.cancellationConfirmationDate.split('T')[0] : '',
         cancellationConfirmationOptionsDate: c.cancellationConfirmationOptionsDate ? c.cancellationConfirmationOptionsDate.split('T')[0] : '',
         wasSpecialCancellation: c.wasSpecialCancellation || false,
+        // Vorgänger-Vertrag
+        previousContractId: c.previousContractId?.toString() || '',
       });
 
       // Load simCards if available
@@ -427,6 +437,7 @@ export default function ContractForm() {
       cancellationConfirmationDate: data.cancellationConfirmationDate ? new Date(data.cancellationConfirmationDate) : null,
       cancellationConfirmationOptionsDate: data.cancellationConfirmationOptionsDate ? new Date(data.cancellationConfirmationOptionsDate) : null,
       wasSpecialCancellation: data.wasSpecialCancellation || false,
+      previousContractId: safeParseInt(data.previousContractId) ?? null,
     };
 
     // Add type-specific details
@@ -540,6 +551,11 @@ export default function ContractForm() {
   const contractCategories = contractCategoriesData?.data?.filter(c => c.isActive).sort((a, b) => a.sortOrder - b.sortOrder) || [];
   const typeOptions = contractCategories.map(c => ({ value: c.code, label: c.name }));
 
+  // Available predecessor contracts (same customer, excluding current contract if editing)
+  const predecessorContracts = (customerContractsData?.data || [])
+    .filter(c => !isEdit || c.id !== parseInt(id!))
+    .sort((a, b) => new Date(b.startDate || 0).getTime() - new Date(a.startDate || 0).getTime());
+
   // Get tariffs for selected provider
   const selectedProvider = providers.find(p => p.id === parseInt(selectedProviderId || '0'));
   const availableTariffs = selectedProvider?.tariffs?.filter(t => t.isActive) || [];
@@ -615,6 +631,19 @@ export default function ContractForm() {
               {...register('salesPlatformId')}
               options={platforms.map((p) => ({ value: p.id, label: p.name }))}
             />
+
+            {/* Vorgänger-Vertrag auswählen (nur wenn Kunde gewählt) */}
+            {customerId && (
+              <Select
+                label="Vorgänger-Vertrag"
+                {...register('previousContractId')}
+                options={predecessorContracts.map((c) => ({
+                  value: c.id,
+                  label: `${c.contractNumber} (${c.type}${c.startDate ? ` - ${new Date(c.startDate).toLocaleDateString('de-DE')}` : ''})`,
+                }))}
+                placeholder="Keinen Vorgänger auswählen"
+              />
+            )}
           </div>
         </Card>