feat(call): migrate from WebRTC to LiveKit

Replace the custom WebRTC implementation with LiveKit for improved
stability and feature support.

- Remove `react-native-webrtc` and custom `WebRTCManager`
- Implement `LiveKitService` for room and track management
- Update `callStore` to handle LiveKit events and connection states
- Refactor `CallScreen` (mobile and web) to use `@livekit/react-native`
  and `VideoView`
- Update WebSocket protocol to use `call_ready` instead of manual SDP/ICE
  exchanges
- Add necessary camera and microphone permissions to `app.json`
- Update Metro and Babel configurations for LiveKit compatibility

app.config.js

@@ -95,7 +95,8 @@ module.exports = {
         // 配置 Web 端别名，避免加载原生模块
         babel: {
           dangerouslyAddModulePathsToTranspile: [
-            'react-native-webrtc',
+            'livekit-client',
+            '@livekit',
           ],
         },
       },