feat: fetch all artist albums with caching, filter by type in handler

- Provider fetches all release groups via paginated browse, no type filter
- Service caches all albums in DB, ensures referenced artists exist first
- Server handler filters by album_types (default: album|ep|single), excludes secondary types
- Add secondary_types to domain, DB schema, and MB types
- Add ErrBadRequest handling for MusicBrainz 400 errors
- Replace migrations with single schema.sql
- Add GetAllByArtistID and SaveAll to album repository

internal/provider/musicbrainz/errors.go

@@ -4,5 +4,6 @@ import "errors"
 
 var (
 	ErrNotFound    = errors.New("not found")
+	ErrBadRequest  = errors.New("bad request")
 	ErrRateLimited = errors.New("rate limited")
 )