- Add POST /api/artists/{id}/refresh to re-fetch metadata from gRPC service
- Add DELETE /api/artists/{id} with cascade delete via PostgreSQL
- Add e2e tests for both flows covering happy path, not found, idempotency
- Extend testutil with GetArtistUpdatedAt, CountAlbumsByArtist, DELETE helper
- Add testutil package with DB/HTTP helpers and cleanup utilities
- Add e2e tests covering artist search, album fetch, sync persistence
- Test idempotent sync, album filtering, library list endpoints
- Requires running PostgreSQL, MetadataService, and API server