The re-add showed no album/single art. Cause: reconstruct returned the full track
from tracks_json AS-IS — and some syncs store tracks_json lean (no album.images),
so the re-added wishlist entry had an empty album.images even though the track's
cover was sitting right there in the track_result's image_url.
Fix: always backfill album.images from the track_result's image_url when the album
has none (and copy the dict so tracks_json isn't mutated). Real album art is kept
when present; the 250px thumb only fills a gap. Verified against a real sync row in
all three cases (full / lean tracks_json / no tracks_json) — album.images now
populated in every one. The wishlist card reads album.images, so the cover shows.
In the dashboard Recent Syncs detail modal, the '→ Wishlist' status on unmatched
tracks is now a button. Clicking it re-adds that exact track to the wishlist with
the SAME context the sync used (source_type='playlist' + the playlist's name/id +
failure_reason), so it's indistinguishable from the original auto-add.
- reconstruct_sync_track_data() (pure, tested): prefers the full cached track from
tracks_json (by source_track_id, then index) so album art/full data carry over;
falls back to the track_result fields; refuses non-'wishlist' rows and rows with
no id (can't re-wishlist a matched/unidentifiable track).
- POST /api/sync/history/<id>/track/<i>/wishlist resolves the entry server-side and
calls the wishlist service; idempotent (reports added vs already-on-wishlist).
- button shows a busy state then '✓ Re-added' / '✓ On wishlist'.
7 pure tests (full-track preference, id-vs-index match, fallback rebuild, non-
wishlist + out-of-range refusal). JS/PY/ruff clean.
