feat: Implement native Android MediaSession and foreground service for TTS playback

- Add `ReaderTtsMediaService` to handle background playback, media controls, and notifications on Android
- Integrate `MediaSessionCompat` to support external media controls and lock screen integration
- Add `ReaderTtsMediaBridge` for synchronized state communication between Kotlin and Flutter
- Update `TtsNotifier` to use the native Android service when available, with a fallback for other platforms
- Implement sentence-level highlighting and tapping to start reading from a specific location
- Update Android manifest with necessary permissions for foreground services and notifications
- Adjust TTS speech rate constants and improve playback health monitoring and recovery logic

lib/features/reader/presentation/tts_player_widget.dart

@@ -30,7 +30,7 @@ class TtsPlayerWidget extends ConsumerWidget {
     final tts = ref.watch(ttsProvider);
     final notifier = ref.read(ttsProvider.notifier);
 
-    const speeds = [0.35, 0.45, 0.55, 0.65, 0.8, 1.0];
+    const speeds = [0.45, 0.675, 0.9, 1.125, 1.35, 1.8];
 
     Future<void> start() async {
       if (tts.status == TtsStatus.paused) {