Add album art search, auto-match and a whole-album tag editor

Search iTunes, Deezer, MusicBrainz, DuckDuckGo and Google for square covers,
embed them and/or save cover.jpg, auto-match covers for albums, and edit an
album's shared tags and track list in one place.

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

internal/api/server.go

@@ -58,6 +58,9 @@ func (s *Server) Handler() http.Handler {
 		r.Use(func(next http.Handler) http.Handler {
 			return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 				limit := int64(1 << 20)
+				if strings.HasSuffix(r.URL.Path, "/art/upload") {
+					limit = 21 << 20
+				}
 				if strings.HasSuffix(r.URL.Path, "/backups/restore-upload") {
 					limit = 20 << 30 // backup zips can be large
 				}
@@ -80,6 +83,13 @@ func (s *Server) Handler() http.Handler {
 			r.Put("/settings", s.handlePutSettings)
 			r.Get("/browse", s.handleBrowse)
 			r.Get("/naming", s.handleNamingInfo)
+			r.Get("/art/settings", s.handleArtSettings)
+			r.Put("/art/settings", s.handlePutArtSettings)
+			r.Get("/art/search", s.handleArtSearch)
+			r.Post("/art/prepare", s.handleArtPrepare)
+			r.Post("/art/upload", s.handleArtUpload)
+			r.Get("/art/prepared/{token}", s.handleArtPrepared)
+			r.Get("/art/thumb", s.handleArtThumb)
 			r.Post("/naming/examples", s.handleNamingExamples)
 			if s.cfg.Backups != nil {
 				s.backupRoutes(r)
@@ -101,6 +111,9 @@ func (s *Server) Handler() http.Handler {
 				r.Post("/bulk/preview", s.handleBulkPreview)
 				r.Post("/bulk", s.handleBulk)
 				r.Get("/files", s.handleFiles)
+				r.Get("/cover", s.handleCover)
+				r.Get("/album", s.handleAlbum)
+				r.Post("/art/auto", s.handleArtAuto)
 				r.Post("/tags/read", s.handleReadTags)
 				r.Post("/tags", s.handleEditTags)
 				r.Post("/organize/preview", s.handleOrganizePreview)