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/src/app.ts

@@ -3,6 +3,7 @@ import cors from '@fastify/cors';
 import helmet from '@fastify/helmet';
 import rateLimit from '@fastify/rate-limit';
 import healthRoutes from './routes/health';
+import importRoutes from './routes/import';
 
 export function buildApp(): FastifyInstance {
   const app: FastifyInstance = Fastify({
@@ -13,6 +14,7 @@ export function buildApp(): FastifyInstance {
   void app.register(helmet);
   void app.register(rateLimit, { max: 1000, timeWindow: '1 minute' });
   void app.register(healthRoutes, { prefix: '/api' });
+  void app.register(importRoutes, { prefix: '/api' });
 
   return app;
 }