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/fsScanner.spec.ts

@@ -0,0 +1,28 @@
+import { describe, it, expect } from 'vitest';
+import path from 'path';
+import { scanDirectory } from '../../src/services/fsScanner';
+
+const fixturesDir = path.join(__dirname, '..', 'fixtures');
+const emptyDir = path.join(fixturesDir, 'empty');
+
+describe('services/fsScanner', () => {
+  it('exporta scanDirectory', () => {
+    expect(typeof scanDirectory).toBe('function');
+  });
+
+  it('carpeta vacía devuelve array', async () => {
+    const res = await scanDirectory(emptyDir);
+    expect(Array.isArray(res)).toBe(true);
+    expect((res as any[]).length).toBe(0);
+  });
+
+  it('detecta simple-rom.bin', async () => {
+    const res = await scanDirectory(fixturesDir);
+    const found = (res as any[]).find(
+      (r: any) => r.filename === 'simple-rom.bin' || r.name === 'simple-rom.bin'
+    );
+    expect(found).toBeTruthy();
+    expect(found.size).toBeGreaterThan(0);
+    expect(found.format).toBeDefined();
+  });
+});