feat: implement Phase 2 - Matches API with real-time notifications

Backend changes:
- Add matches API routes (POST, GET, PUT, DELETE)
- Create/accept/reject match requests
- Auto-create private chat rooms on match acceptance
- Socket.IO notifications for match events (received, accepted, cancelled)
- Users join personal rooms (user_{id}) for notifications

Frontend changes:
- Add MatchesPage component with inbox UI
- Matches navigation link with notification badge
- Real-time match request count updates
- Accept/reject match functionality
- Filter matches by status (all/pending/accepted)
- Integrate match requests in EventChatPage (UserPlus button)

Features:
- Send match requests to event participants
- Accept incoming match requests
- Real-time notifications via Socket.IO
- Automatic private chat room creation
- Match status tracking (pending/accepted/completed)
- Authorization checks (only participants can match)
- Duplicate match prevention

backend/src/socket/index.js

@@ -63,6 +63,11 @@ function initializeSocket(httpServer) {
   io.on('connection', (socket) => {
     console.log(`✅ User connected: ${socket.user.username} (${socket.id})`);
 
+    // Join user's personal room for notifications
+    const userRoom = `user_${socket.user.id}`;
+    socket.join(userRoom);
+    console.log(`📬 ${socket.user.username} joined personal room: ${userRoom}`);
+
     // Join event room
     socket.on('join_event_room', async ({ slug }) => {
       try {