- In `track_metadata.rs`, implement fallback logic for lazy PKs: first try real_pk, then fallback to lazy_pk for metadata keys seeded before download.
- In `db.rs`, add debug logging after migration to track remaining metadata under lazy_pk.
- In `source.rs` (Qobuz):
- Detect and repair playlists with missing cache entries by forcing refresh when `items.len() < total`.
- Preserve original track order after parallel processing by attaching and sorting on original index.
- Handle missing performer/cover gracefully with warnings and provider fallback.
- In `metadata_cache.rs` (Radio France), simplify logging and improve test coverage for expiration logic.
- In `cache.rs`, add debug/warning logs when metadata or cover seeding fails during lazy caching.
