_resolve_album_tracklist gains a Fallback -1: if the album has a pinned
canonical (source, album_id), use it before the existing 6-level cascade — so
Track Number Repair resolves the SAME release the Reorganizer does (Stage 3) and
the two stop contradicting each other (#765, the Spotify-4 vs MusicBrainz-3
conflict).
Gated + additive: the entire existing cascade is untouched for albums without a
canonical, so this job's all-01-album rescue (which relies on the MusicBrainz/
AudioDB fallbacks for albums with no DB source ID) is fully preserved — that's
the regression we explicitly refused to take in a reactive fix.
New helper _lookup_canonical_from_db() mirrors _lookup_album_ids_from_db
(file-path -> track -> album), returns None when no DB / no match / columns
absent / unresolved.
Tests: tests/test_track_repair_canonical.py (4) — returns canonical when pinned,
None when unresolved / file untracked / no DB. Existing track_number_repair
tests still pass (no regression).
