refactor: Remove scripts section from backend package.json

- Remove npm start script configuration
- Simplify package.json to only include dependencies
- Users will run server with direct node command instead

Author: Iswanna

chat-app/backend/package.json

@@ -1,8 +1,5 @@
 {
   "type": "module",
-  "scripts": {
-    "start": "node server.js"
-  },
   "dependencies": {
     "cors": "^2.8.6",
     "express": "^5.2.1"