Backend:
- Add get_artist_tracks command for fetching artist's popular tracks
Frontend:
- Fallback to artist's popular tracks when tracks_appears_on is sparse
- Remove card hover movement, only image moves up on hover
- Add hover overlay with (add to queue) (play) (play next) buttons
- Use playlist.svg icon for playlist cards and glyph
- Radio glyph shown by default, replaced by action buttons on hover
- Fix icon sizes: QBZ (22px) vs Qobuz (18px) for visual balance
- Track playlist.svg asset
