added contract history

backend/prisma/migrations/20260208174811_add_contract_history/migration.sql

@@ -0,0 +1,15 @@
+-- CreateTable
+CREATE TABLE `ContractHistoryEntry` (
+    `id` INTEGER NOT NULL AUTO_INCREMENT,
+    `contractId` INTEGER NOT NULL,
+    `title` VARCHAR(191) NOT NULL,
+    `description` TEXT NULL,
+    `isAutomatic` BOOLEAN NOT NULL DEFAULT false,
+    `createdBy` VARCHAR(191) NOT NULL,
+    `createdAt` DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3),
+
+    PRIMARY KEY (`id`)
+) DEFAULT CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;
+
+-- AddForeignKey
+ALTER TABLE `ContractHistoryEntry` ADD CONSTRAINT `ContractHistoryEntry_contractId_fkey` FOREIGN KEY (`contractId`) REFERENCES `Contract`(`id`) ON DELETE CASCADE ON UPDATE CASCADE;

backend/prisma/schema.prisma

@@ -566,11 +566,25 @@ model Contract {
 
   tasks                   ContractTask[]
   assignedEmails          CachedEmail[]   // Zugeordnete E-Mails aus dem E-Mail-Client
+  historyEntries          ContractHistoryEntry[]
 
   createdAt               DateTime        @default(now())
   updatedAt               DateTime        @updatedAt
 }
 
+// ==================== CONTRACT HISTORY ====================
+
+model ContractHistoryEntry {
+  id          Int      @id @default(autoincrement())
+  contractId  Int
+  contract    Contract @relation(fields: [contractId], references: [id], onDelete: Cascade)
+  title       String                     // Kurzbeschreibung (z.B. "Folgevertrag erstellt", "kWh auf 18000 erhöht")
+  description String?  @db.Text          // Längere Beschreibung (optional)
+  isAutomatic Boolean  @default(false)   // true = automatisch erstellt, false = manuell
+  createdBy   String                     // E-Mail des Erstellers
+  createdAt   DateTime @default(now())
+}
+
 // ==================== CONTRACT TASKS ====================
 
 enum ContractTaskStatus {