feat(call): implement CallKeep integration and enhance group call support

Integrate `expo-callkit-telecom` to support native system call handling (answering, ending, and muting via system UI). This includes a new `callKeepService` and a `CallKeepBootstrap` component to manage the lifecycle of system call events.

Additionally, improves the calling experience by:
- Adding support for group calls with participant tracking and UI indicators.
- Enhancing LiveKit integration by replacing polling with event-driven video track synchronization.
- Updating `WebSocketService` to prevent disconnection when the app enters the background during an active call.
- Adding new WebSocket message types for participant join/leave events and group invites.
- Refining call UI components (`CallScreen`, `FloatingCallWindow`, `IncomingCallModal`) for better visual feedback and safe area handling.

Refactor LiveKit service to use event-driven updates for local and remote tracks, improving performance and reliability.

app.json

@@ -153,6 +153,7 @@
         }
       ],
       "./plugins/withHuaweiPush",
+      "expo-callkit-telecom",
       "expo-status-bar"
     ],
     "extra": {