feat: a release catalogue from MusicBrainz; request search asks it directly (M502 #5519)

Minstrel keeps its own record of what artists have released, read from
MusicBrainz, so the wanted list, search and import no longer need Lidarr.

- internal/musicbrainz: searches (artists, release groups, recordings) and
  browses (an artist's release groups; a group's releases with track lists).
  One process-wide pacer at 1.1s, shared with tag enrichment, because
  MusicBrainz's limit is per address. A 503 throttle is retried.
- Migration 0080: mb_artists, mb_release_groups, mb_artist_release_groups
  (a collaboration belongs to each credited artist), mb_releases,
  mb_release_tracks.
- internal/catalogue: Discography and Releases serve the held copy and
  re-read it when older than 7 or 30 days. An unreachable MusicBrainz
  serves the stale copy, marked. An hourly pass re-reads due artists.
- Art for what isn't held comes through /api/catalogue/art from the
  enabled cover-art sources (Cover Art Archive by release group, then the
  name-based sources) and is kept on disk, so the browser never fetches a
  third-party host. A miss is a 404 and the card shows its icon.
- Request search moves from /api/lidarr/search to /api/catalogue/search,
  with the same response shape. Albums are release groups, and "in
  library" matches albums.release_group_mbid. A 10-minute cache absorbs
  search-as-you-type. Discover suggestions point at the art endpoint
  instead of looking up Lidarr.
- Android calls the new path and loads Discover art through ServerImage.
  Installed builds older than this one lose Discover search until they
  update (no compatibility path, rule 22).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/api/api.go

@@ -15,6 +15,7 @@ import (
 
 	"git.fabledsword.com/bvandeusen/minstrel/internal/acquire"
 	"git.fabledsword.com/bvandeusen/minstrel/internal/auth"
+	"git.fabledsword.com/bvandeusen/minstrel/internal/catalogue"
 	"git.fabledsword.com/bvandeusen/minstrel/internal/config"
 	"git.fabledsword.com/bvandeusen/minstrel/internal/coverart"
 	"git.fabledsword.com/bvandeusen/minstrel/internal/eventbus"
@@ -72,6 +73,9 @@ func Mount(r chi.Router, pool *pgxpool.Pool, logger *slog.Logger, events *playev
 		loudnessSettings:    loudSettings,
 		acoustIDLookup:      acoustIDLookup,
 		acquisition:         acquire.NewStore(pool),
+		catalogue:           catalogue.New(pool, nil, logger),
+		catalogueSearches:   newSearchCache(),
+		catalogueArt:        catalogue.NewArt(dataDir, artSources(coverSettings)),
 		leveled:             newLeveledRenderer(dataDir, loudSettings, logger),
 		librarySize:         recommendation.NewLibrarySize(nil),
 		loginGuard:          auth.NewLoginGuard(),
@@ -184,7 +188,11 @@ func Mount(r chi.Router, pool *pgxpool.Pool, logger *slog.Logger, events *playev
 			authed.Get("/likes/artists", h.handleListLikedArtists)
 			authed.Get("/likes/ids", h.handleGetLikedIDs)
 
-			authed.Get("/lidarr/search", h.handleLidarrSearch)
+			// The release catalogue (M502 #5519): request search asks
+			// MusicBrainz, and art for what isn't held comes through
+			// Minstrel from the enabled cover-art sources.
+			authed.Get("/catalogue/search", h.handleCatalogueSearch)
+			authed.Get("/catalogue/art/{kind}/{mbid}", h.handleCatalogueArt)
 
 			authed.Post("/requests", h.handleCreateRequest)
 			authed.Get("/requests", h.handleListRequests)
@@ -385,6 +393,13 @@ type handlers struct {
 	acoustIDLookup *library.AcoustIDLookupWorker
 	// acquisition is the operator's indexers and download clients (M502).
 	acquisition *acquire.Store
+	// catalogue is the release catalogue read from MusicBrainz, and
+	// catalogueArt the images for what isn't held (M502 #5519).
+	catalogue    *catalogue.Service
+	catalogueArt *catalogue.Art
+	// catalogueSearches reuses recent MusicBrainz answers; nil asks every
+	// time, which is what handler tests get.
+	catalogueSearches *searchCache
 	// leveled renders the leveled streams handed to Sonos/UPnP speakers
 	// (M464 #5001). Nil when its cache directory cannot be made: a level
 	// request then gets the plain stream.
@@ -427,3 +442,13 @@ func newLeveledRenderer(dataDir string, settings *library.LoudnessSettingsServic
 	}
 	return r
 }
+
+// artSources hands the art cache the cover-art settings, or nothing when
+// there are none: a nil *SettingsService inside the interface would not
+// compare equal to nil and would be called.
+func artSources(s *coverart.SettingsService) catalogue.ArtSources {
+	if s == nil {
+		return nil
+	}
+	return s
+}