feat: implement dockerfiles and improve cors configuration

backend/src/server.ts

@@ -10,7 +10,11 @@ import routes from './routes';
 
 const app = express();
 
-app.use(cors());
+const allowedOrigins = (process.env.CORS_ORIGIN || 'http://localhost:3000')
+    .split(',')
+    .map(origin => origin.trim());
+
+app.use(cors({ origin: allowedOrigins }));
 app.use(express.json());
 
 app.use('/api', routes);