added Mercado Pago integration with new payment handling functions and updated app routing

src/app.js

@@ -5,6 +5,7 @@ import { fileURLToPath } from "url";
 
 import { createSimulatorRouter } from "./routes/simulator.js";
 import { createEvolutionRouter } from "./routes/evolution.js";
+import { createMercadoPagoRouter } from "./routes/mercadoPago.js";
 
 export function createApp({ tenantId }) {
   const app = express();
@@ -21,6 +22,7 @@ export function createApp({ tenantId }) {
   // --- Integraciones / UI ---
   app.use(createSimulatorRouter({ tenantId }));
   app.use(createEvolutionRouter());
+  app.use("/payments/meli", createMercadoPagoRouter());
 
   // Home (UI)
   app.get("/", (req, res) => {