feat: add plan enforcement middleware (subscription, CFDI limits, feature gates)

- checkPlanLimits: blocks writes when subscription inactive
- checkCfdiLimit: enforces per-plan CFDI count limits
- requireFeature: gates reportes/alertas/calendario by plan tier
- All cached with 5-min TTL, invalidated via PM2 messaging

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

apps/api/src/routes/alertas.routes.ts

@@ -1,12 +1,16 @@
 import { Router, type IRouter } from 'express';
 import { authenticate } from '../middlewares/auth.middleware.js';
 import { tenantMiddleware } from '../middlewares/tenant.middleware.js';
+import { checkPlanLimits } from '../middlewares/plan-limits.middleware.js';
+import { requireFeature } from '../middlewares/feature-gate.middleware.js';
 import * as alertasController from '../controllers/alertas.controller.js';
 
 const router: IRouter = Router();
 
 router.use(authenticate);
 router.use(tenantMiddleware);
+router.use(checkPlanLimits);
+router.use(requireFeature('alertas'));
 
 router.get('/', alertasController.getAlertas);
 router.get('/stats', alertasController.getStats);