- Move the metadata and MusicBrainz-related tests into a dedicated tests/metadata subfolder.
- Keep the rest of the suite flat for now.
- Preserve the existing test filenames so the change stays organizational rather than behavioral.
- Move album-track resolution into metadata_service
- Use the configured provider order instead of Spotify-first branching
- Switch the frontend to the unified /api/album/<id>/tracks endpoint
- Add tests for source-priority lookup, DB resolution, and formatting