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/extractions/extractions.service.spec.ts

@@ -0,0 +1,61 @@
+import { NotFoundException } from '@nestjs/common';
+import { ExtractionsService } from './extractions.service';
+import { PrismaService } from '../prisma/prisma.service';
+import { AuditLogService } from '../audit/audit-log.service';
+
+describe('ExtractionsService', () => {
+  let service: ExtractionsService;
+  let prisma: {
+    extraction: { findUnique: jest.Mock };
+    $transaction: jest.Mock;
+  };
+  let auditLog: { record: jest.Mock };
+  let tx: {
+    extraction: { create: jest.Mock };
+    extractionHarvest: { createMany: jest.Mock };
+  };
+
+  const extraction = { id: 'extraction-1', date: new Date() };
+
+  beforeEach(() => {
+    tx = {
+      extraction: { create: jest.fn().mockResolvedValue(extraction) },
+      extractionHarvest: { createMany: jest.fn() },
+    };
+    prisma = {
+      extraction: { findUnique: jest.fn() },
+      $transaction: jest.fn((callback: (txArg: typeof tx) => unknown) =>
+        callback(tx),
+      ),
+    };
+    auditLog = { record: jest.fn() };
+    service = new ExtractionsService(
+      prisma as unknown as PrismaService,
+      auditLog as unknown as AuditLogService,
+    );
+  });
+
+  it('findById throws NotFoundException when missing', async () => {
+    prisma.extraction.findUnique.mockResolvedValue(null);
+    await expect(service.findById('missing')).rejects.toBeInstanceOf(
+      NotFoundException,
+    );
+  });
+
+  it('create links every harvest to the extraction inside a transaction', async () => {
+    prisma.extraction.findUnique.mockResolvedValue(extraction);
+
+    await service.create(
+      { date: '2026-07-05', harvestIds: ['harvest-1', 'harvest-2'] },
+      'user-1',
+    );
+
+    const [[createArg]] = tx.extractionHarvest.createMany.mock.calls as [
+      [{ data: { extractionId: string; harvestId: string }[] }],
+    ];
+    expect(createArg.data).toEqual([
+      { extractionId: extraction.id, harvestId: 'harvest-1' },
+      { extractionId: extraction.id, harvestId: 'harvest-2' },
+    ]);
+  });
+});