Phase 2 backend: LiveKit voice integration

Backend:
- internal/voice/client.go: LiveKit token generation, room management, participant listing
- internal/voice/handlers.go: POST /voice/token, GET /voice/rooms/{roomID}/participants
- internal/gateway/events.go: added VOICE_JOIN, VOICE_LEAVE, VOICE_MUTE, VOICE_DEAFEN events
- cmd/server/main.go: wired voice client and routes under /api/v1/voice
- Docker: livekit.yaml config verified

Frontend deps:
- Added livekit-client and @livekit/components-react packages

web/package.json

@@ -10,7 +10,8 @@
     "preview": "vite preview"
   },
   "dependencies": {
-    "livekit-client": "^2.3.1",
+    "@livekit/components-react": "^2.9.21",
+    "livekit-client": "^2.20.0",
     "react": "^18.3.1",
     "react-dom": "^18.3.1",
     "react-router-dom": "^6.23.1",