Repair jobs were making Spotify API calls without checking the global
rate limit ban, causing them to churn through every item getting rejected
one by one during a ban. Now all Spotify calls in repair jobs check
context.is_spotify_rate_limited() first and skip/fallback gracefully.
- Add is_spotify_rate_limited() helper to JobContext (base.py)
- Guard calls in track_number_repair, album_completeness,
missing_cover_art, and metadata_gap_filler
- Jobs fall through to iTunes/MusicBrainz fallbacks when rate-limited
