Distinct circular song cards with jump-to-album badge

[Psychotoxical]

Summary

• Single-track cards looked identical to album tiles, so clicking the body read as album behaviour even though it starts playback. They now use a round, vinyl-style cover (square stays album-only) so the two are unmistakable.
• New To album badge under the artist navigates to the track's album (via the shared useNavigateToAlbum helper). Card click still plays; the badge is the explicit nav path, so the Play button is no longer redundant.
• Round-cover treatment factored into a reusable .cover-circle utility (layout/cover-art.css) instead of a one-off; carries the paint-stability hints round image clipping needs on WebKitGTK.
• tracks.toAlbum added across all 9 locales.

Test plan

• Home and Tracks discovery rails: track cards render as circular discs, album/artist cards unchanged.
• Clicking a track card still plays; the badge opens the track's album and back returns to the rail.
• Badge hidden when a track has no album id.

Notes

• Frontend only — no Tauri boundary change.