Display parental_warning badge (E icon) next to track titles in all
views: TrackRow, QueuePanel, NowPlayingBar, ImmersivePlayer with all
13 visualizer panels, MiniPlayer surfaces, and AlbumDetailView.
Propagate parental_warning field through the full data chain from
Rust backend (qbz-models, queue, commands_v2, session_store, API
server) to frontend stores, adapters, and UI components. Badge uses
CSS mask technique with explicit.svg for theme compatibility.