fix(referral-service): 修复端口配置使用 APP_PORT

backend/services/referral-service/src/main.ts

@@ -47,7 +47,7 @@ async function bootstrap() {
     logger.log('Swagger documentation available at /api/docs');
   }
 
-  const port = process.env.PORT || 3002;
+  const port = parseInt(process.env.APP_PORT || '3004', 10);
   await app.listen(port);
   logger.log(`Referral Service is running on port ${port}`);
 }