feat(backend): Webhooks mit HMAC-signierter Auslieferung (Modul 28)

WebhooksModule (WebhookSubscription: URL, Events, Secret, aktiv) mit
Event-Dispatcher, angehaengt an 10 Ereignisse in 8 bestehenden Services
(colony.created, inspection.created, queen.created, queen.replaced,
harvest.created, batch.created, batch.updated, product.stock_changed,
task.created, task.completed). Auslieferung ist best-effort und blockiert
die ausloesende Anfrage nicht bei Fehlern.

ApiCore-Backend/src/tasks/tasks.service.spec.ts

@@ -2,6 +2,7 @@ import { NotFoundException } from '@nestjs/common';
 import { TasksService } from './tasks.service';
 import { PrismaService } from '../prisma/prisma.service';
 import { AuditLogService } from '../audit/audit-log.service';
+import { WebhooksService } from '../webhooks/webhooks.service';
 
 describe('TasksService', () => {
   let service: TasksService;
@@ -27,9 +28,11 @@ describe('TasksService', () => {
       },
     };
     auditLog = { record: jest.fn() };
+    const webhooks = { dispatch: jest.fn().mockResolvedValue(undefined) };
     service = new TasksService(
       prisma as unknown as PrismaService,
       auditLog as unknown as AuditLogService,
+      webhooks as unknown as WebhooksService,
     );
   });