feat: import job runner in-memory

- Añade ImportRunner en memoria con concurrencia configurable
- Tests TDD para enqueue, concurrencia y comportamiento tras stop
- Actualiza /api/import/scan para encolar jobs y registrar errores
- Ajusta tsconfig.json para incluir tests en comprobaciones de tipo

backend/tests/services/checksumService.spec.ts

@@ -0,0 +1,21 @@
+import { describe, it, expect } from 'vitest';
+import path from 'path';
+import { computeHashes } from '../../src/services/checksumService';
+
+const fixturesDir = path.join(__dirname, '..', 'fixtures');
+const simpleRom = path.join(fixturesDir, 'simple-rom.bin');
+
+describe('services/checksumService', () => {
+  it('exporta computeHashes', () => {
+    expect(typeof computeHashes).toBe('function');
+  });
+
+  it('calcula hashes', async () => {
+    const meta = await computeHashes(simpleRom);
+    expect(meta).toBeDefined();
+    expect(meta.size).toBeGreaterThan(0);
+    expect(meta.md5).toBeDefined();
+    expect(meta.sha1).toBeDefined();
+    expect(meta.crc32).toBeDefined();
+  });
+});