feat(backend): Ernten- und Schleuderungs-Module (Modul 10)

HarvestsModule und ExtractionsModule als Fundament der
Rückverfolgbarkeitskette: eine Ernte kann mehrere Völker umfassen,
eine Schleuderung mehrere Ernten zusammenführen.

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

@@ -0,0 +1,65 @@
+import { NotFoundException } from '@nestjs/common';
+import { HarvestsService } from './harvests.service';
+import { PrismaService } from '../prisma/prisma.service';
+import { AuditLogService } from '../audit/audit-log.service';
+
+describe('HarvestsService', () => {
+  let service: HarvestsService;
+  let prisma: {
+    harvest: { findUnique: jest.Mock };
+    $transaction: jest.Mock;
+  };
+  let auditLog: { record: jest.Mock };
+  let tx: {
+    harvest: { create: jest.Mock };
+    harvestColony: { createMany: jest.Mock };
+  };
+
+  const harvest = { id: 'harvest-1', apiaryId: 'apiary-1', date: new Date() };
+
+  beforeEach(() => {
+    tx = {
+      harvest: { create: jest.fn().mockResolvedValue(harvest) },
+      harvestColony: { createMany: jest.fn() },
+    };
+    prisma = {
+      harvest: { findUnique: jest.fn() },
+      $transaction: jest.fn((callback: (txArg: typeof tx) => unknown) =>
+        callback(tx),
+      ),
+    };
+    auditLog = { record: jest.fn() };
+    service = new HarvestsService(
+      prisma as unknown as PrismaService,
+      auditLog as unknown as AuditLogService,
+    );
+  });
+
+  it('findById throws NotFoundException when missing', async () => {
+    prisma.harvest.findUnique.mockResolvedValue(null);
+    await expect(service.findById('missing')).rejects.toBeInstanceOf(
+      NotFoundException,
+    );
+  });
+
+  it('create links every colony to the harvest inside a transaction', async () => {
+    prisma.harvest.findUnique.mockResolvedValue(harvest);
+
+    await service.create(
+      {
+        apiaryId: 'apiary-1',
+        date: '2026-07-01',
+        colonyIds: ['colony-1', 'colony-2'],
+      },
+      'user-1',
+    );
+
+    const [[createArg]] = tx.harvestColony.createMany.mock.calls as [
+      [{ data: { harvestId: string; colonyId: string }[] }],
+    ];
+    expect(createArg.data).toEqual([
+      { harvestId: harvest.id, colonyId: 'colony-1' },
+      { harvestId: harvest.id, colonyId: 'colony-2' },
+    ]);
+  });
+});