feat(player): notification favorite via MediaControl.custom (6c)

Adds a heart action to the media notification implemented as a custom
control + customAction handler — NOT setRating, which is broken
upstream (audio_service #376: onSetRating never fires from a
notification tap) and previously blanked the Pixel Watch.

- res/drawable/ic_stat_favorite{,_border}.xml: white 24dp vector hearts
- audio_handler: favorite MediaControl.custom in _broadcastState
  (icon/label toggle by LikeBridge state; kept out of
  androidCompactActionIndices so compact/lock + Wear transport are
  unchanged); customAction override (Future<dynamic>, matches base)
  toggles the like then re-broadcasts; refreshFavoriteControl()
- player_provider: cascade refreshFavoriteControl into the likedIds
  listener so liking from TrackRow/kebab/SSE flips the notification heart

Reliable on phone notification + lock screen; Wear/Auto display of a
non-transport custom action is platform-dependent (not a bug).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

flutter_client/android/app/src/main/res/drawable/ic_stat_favorite.xml

@@ -0,0 +1,10 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:viewportWidth="24"
+    android:viewportHeight="24"
+    android:tint="#FFFFFFFF">
+  <path
+      android:fillColor="#FFFFFFFF"
+      android:pathData="M12,21.35l-1.45,-1.32C5.4,15.36 2,12.28 2,8.5 2,5.42 4.42,3 7.5,3c1.74,0 3.41,0.81 4.5,2.09C13.09,3.81 14.76,3 16.5,3 19.58,3 22,5.42 22,8.5c0,3.78 -3.4,6.86 -8.55,11.54L12,21.35z"/>
+</vector>

flutter_client/android/app/src/main/res/drawable/ic_stat_favorite_border.xml

@@ -0,0 +1,10 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:viewportWidth="24"
+    android:viewportHeight="24"
+    android:tint="#FFFFFFFF">
+  <path
+      android:fillColor="#FFFFFFFF"
+      android:pathData="M16.5,3c-1.74,0 -3.41,0.81 -4.5,2.09C10.91,3.81 9.24,3 7.5,3 4.42,3 2,5.42 2,8.5c0,3.78 3.4,6.86 8.55,11.54L12,21.35l1.45,-1.32C18.6,15.36 22,12.28 22,8.5 22,5.42 19.58,3 16.5,3zM12.1,18.55l-0.1,0.1 -0.1,-0.1C7.14,14.24 4,11.39 4,8.5 4,6.5 5.5,5 7.5,5c1.54,0 3.04,0.99 3.57,2.36h1.87C13.46,5.99 14.96,5 16.5,5c2,0 3.5,1.5 3.5,3.5 0,2.89 -3.14,5.74 -7.9,10.05z"/>
+</vector>