fix(cors): refine CORS handling for OPTIONS requests

- Updated CORS middleware to explicitly handle OPTIONS requests, ensuring proper preflight response and improving API request handling.

backend/app.js

@@ -83,7 +83,12 @@ const corsOptions = {
 };
 
 app.use(cors(corsOptions));
-app.options('*', cors(corsOptions));
+app.use((req, res, next) => {
+  if (req.method === 'OPTIONS') {
+    return cors(corsOptions)(req, res, next);
+  }
+  return next();
+});
 app.use(express.json()); // To handle JSON request bodies
 
 app.use('/api/chat', chatRouter);