- Create Hub with register/unregister/broadcast, room/user index
- Create Client with readPump/writePump goroutines, 30s ping keepalive
- Define all 18 incoming + 18 outgoing message types matching Rust protocol
- Add ValidateChatToken to ChatService for JWT validation
- Update WSUrl from /ws to /api/v1/ws
- Register GET /api/v1/ws endpoint in router
- Create ChatWebSocketHandler for WebSocket upgrade and auth
