Function player_on_playback_ended 

pub async fn player_on_playback_ended(
    player: State<'_, PlayerStateWrapper>,
    repository_manager: State<'_, RepositoryManagerWrapper>,
    db: State<'_, DatabaseWrapper>,
    item_id: Option<String>,
    repository_handle: Option<String>,
) -> Result<(), String>

Handle playback ended event - triggers autoplay decision logic This is called from:

• Frontend when HTML5 video ends (Linux/desktop) - passes itemId + repositoryHandle for the video
• Frontend when audio track ends via backend event - no itemId/repositoryHandle needed
• Android JNI callback also triggers this logic directly

TRACES: UR-023, UR-026, UR-040 | DR-047, DR-052, DR-129