feat: native Android audio via Media3 ExoPlayer + full NSBridge JS adapter

- Replace legacy MediaBrowserServiceCompat/MediaSessionCompat with
  Media3 MediaSessionService (MusicService.kt) + ExoPlayer set to
  WAKE_MODE_NETWORK — holds WakeLock + WifiLock through Doze so audio
  plays uninterrupted on locked screen
- Media3 manages the notification; no manual NotificationCompat.Builder
  → no disappear/reappear flicker when skipping tracks
- Full bidirectional bridge:
    JS → native: window.NSBridge.* (WebBridge.kt, 13 methods)
    Native → JS: window.NSPlayer.* callbacks (onReady, onTrackChanged,
      onPositionUpdate, onPlaybackStateChanged, onQueueEnded, onError)
- player.js: progressive enhancement — all playback routes through
  NSBridge when running inside the wrapper, falls back to S.audio on
  plain PWA/browser; removes all window.Android.* calls
- main.js: guard _onForeground mediaSession playbackState setter behind
  !window.NSBridge so native Media3 session is never stomped
- ProGuard rules updated to keep WebBridge @JavascriptInterface methods
  and Media3 classes
- bridge-test.html: manual integration test page for every bridge method

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

android/app/build.gradle.kts

@@ -0,0 +1,48 @@
+plugins {
+    alias(libs.plugins.android.application)
+    alias(libs.plugins.kotlin.android)
+}
+
+android {
+    namespace = "com.novasonic.app"
+    compileSdk = 34
+
+    defaultConfig {
+        applicationId = "com.novasonic.app"
+        minSdk = 24
+        targetSdk = 34
+        versionCode = 1
+        versionName = "1.0"
+        buildConfigField("String", "NOVASONIC_URL", "\"https://music.asianxpolish.duckdns.org\"")
+    }
+
+    buildFeatures {
+        buildConfig = true
+    }
+
+    buildTypes {
+        release {
+            isMinifyEnabled = true
+            proguardFiles(getDefaultProguardFile("proguard-android-optimize.txt"), "proguard-rules.pro")
+        }
+    }
+
+    compileOptions {
+        sourceCompatibility = JavaVersion.VERSION_1_8
+        targetCompatibility = JavaVersion.VERSION_1_8
+    }
+
+    kotlinOptions {
+        jvmTarget = "1.8"
+    }
+}
+
+dependencies {
+    implementation(libs.androidx.core.ktx)
+    implementation(libs.androidx.appcompat)
+    implementation(libs.material)
+    implementation(libs.media3.exoplayer)
+    implementation(libs.media3.session)
+    implementation(libs.media3.common)
+    implementation(libs.kotlinx.coroutines.android)
+}