feat: add player screen to TV app via compose navigation

- Add PlayerRoute to the Route sealed interface
- Refactor PlayerViewModel to expose loadMedia() for external callers
- Add onPlay() to EpisodeScreenViewModel and MovieScreenViewModel
- Wire play/resume buttons in TV episode and movie screens
- Create TvPlayerScreen with TV-optimized controls: seek bar, playback
  buttons, track selection panels, queue panel, and state cards
- Register PlayerRoute in TvRouteEntryBuilder and TvNavigationModule
- Add media3-ui dependency to app-tv module

core/data/src/main/java/hu/bbara/purefin/core/data/navigation/Route.kt

@@ -21,4 +21,7 @@ sealed interface Route : NavKey {
 
     @Serializable
     data object LoginRoute : Route
+
+    @Serializable
+    data class PlayerRoute(val mediaId: String) : Route
 }