Implement dual-source architecture where iTunes serves as always-available
primary source and Spotify as preferred source when authenticated.
- Make watchlist scans provider-aware (manual and auto paths)
- Update discovery pool population to process both sources
- Update recent albums caching for both sources
- Create source-specific curated playlists (Fresh Tape, Archives)
- Add on-the-fly iTunes ID resolution for similar artists
- Add iTunes ID check to similar artists freshness validation
- Fix sqlite3.Row compatibility in personalized playlists
- Fix iTunes ISO 8601 date format parsing
- Update API endpoints to serve source-appropriate data
This ensures the app remains fully functional if Spotify becomes
unavailable (rate limits, auth issues, bans) by seamlessly falling
back to iTunes data that has been building in parallel.
4319d440ee