insert_qobuz_cached_track_direct was hardcoding track_number to 0,
causing all imported tracks to show wrong numbers. Now accepts
track_number and disc_number params, and both callers (backfill
downloads and offline cache sync) extract metadata from the audio
file via MetadataExtractor before inserting.
Also fix LocalLibraryView to use || instead of ?? for track_number
fallback, so 0 correctly falls back to index-based numbering.
Closes#147
vicrodh
786ce883ac