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

android/app/build.gradle.kts

@@ -4,6 +4,7 @@ import java.util.Properties
 plugins {
     id("com.android.application")
     id("kotlin-android")
+    id("kotlin-parcelize")
     // The Flutter Gradle Plugin must be applied after the Android and Kotlin Gradle plugins.
     id("dev.flutter.flutter-gradle-plugin")
     id("com.google.gms.google-services")
@@ -66,6 +67,10 @@ android {
     }
 }
 
+dependencies {
+    implementation("androidx.media:media:1.7.0")
+}
+
 flutter {
     source = "../.."
 }