fix: upgrade to react-native-track-player 5.0.0-alpha0 (Media3/New Arch)

- RNTP 4.1.2 used ExoPlayer 2.x which is incompatible with RN 0.85.3
- RNTP 5.0.0-alpha0 uses androidx.media3 and supports New Architecture
- Remove newArchEnabled:false from app.json (New Arch is default)
- Remove Kotlin null safety patch (no longer needed)
- Remove patch-package (no more patches required)
- Fix getState() -> getPlaybackState() API rename in player.js
- Add babel.config.js with babel-preset-expo

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

mobile/app.json

@@ -20,7 +20,6 @@
         "foregroundImage": "./assets/android-icon-foreground.png"
       },
       "package": "com.honeyy.novasonic",
-      "newArchEnabled": false,
       "permissions": [
         "android.permission.FOREGROUND_SERVICE",
         "android.permission.FOREGROUND_SERVICE_MEDIA_PLAYBACK"