fix(socket): improve connection stability with heartbeat and auto-reconnect

- Backend: Add pingInterval (25s) and pingTimeout (60s) for better keep-alive
- Frontend: Increase reconnection attempts to Infinity (keep trying forever)
- Frontend: Add reconnect event handlers to rejoin rooms after reconnection
- Frontend: Check initial connection state when reusing socket instance

backend/src/socket/index.js

@@ -21,6 +21,12 @@ function initializeSocket(httpServer) {
       origin: process.env.CORS_ORIGIN || 'http://localhost:8080',
       credentials: true,
     },
+    // Ping/pong heartbeat configuration
+    pingInterval: 25000,  // Send ping every 25 seconds
+    pingTimeout: 60000,   // Wait 60 seconds for pong before considering disconnected
+    // Allow upgrade from polling to websocket
+    transports: ['polling', 'websocket'],
+    allowUpgrades: true,
   });
 
   // Authentication middleware for Socket.IO