feat: Add sorting options for Artists

Include both `Album Count` and `Random` sortings for the Artists page.

This change also fixes the Artist search feature in Jellyfin, which was
broken because of an open issue on Jellyfin [1]. The current workaround
is to do the filtering locally after receiving all results from Jellyfin
API.

Also, as the Jellyfin API doesn't include a sorting option for
`AlbumCount`, we need to disable pagination when that option is
selected, to receive all artists, and run the sorting locally.

[1] Related issue: https://github.com/jellyfin/jellyfin/issues/8222

backend/mediaprovider/subsonic/artistiterator.go

@@ -2,7 +2,9 @@ package subsonic
 
 import (
 	"log"
+	"math/rand"
 	"slices"
+	"time"
 
 	"golang.org/x/text/collate"
 	"golang.org/x/text/language"
@@ -14,12 +16,16 @@ import (
 )
 
 const (
-	ArtistSortNameAZ string = "Name (A-Z)"
+	ArtistSortAlbumCount string = "Album Count"
+	ArtistSortNameAZ     string = "Name (A-Z)"
+	ArtistSortRandom     string = "Random"
 )
 
 func (s *subsonicMediaProvider) ArtistSortOrders() []string {
 	return []string{
+		ArtistSortAlbumCount,
 		ArtistSortNameAZ,
+		ArtistSortRandom,
 	}
 }
 
@@ -35,6 +41,16 @@ func (s *subsonicMediaProvider) IterateArtists(sortOrder string, filter mediapro
 		sortOrder = ArtistSortNameAZ // default
 	}
 	switch sortOrder {
+	case ArtistSortAlbumCount:
+		return s.baseArtistIterFromSimpleSortOrder(
+			func(artists []*subsonic.ArtistID3) []*subsonic.ArtistID3 {
+				slices.SortStableFunc(artists, func(a, b *subsonic.ArtistID3) int {
+					return b.AlbumCount - a.AlbumCount
+				})
+				return artists
+			},
+			filter,
+		)
 	case ArtistSortNameAZ:
 		return s.baseArtistIterFromSimpleSortOrder(
 			func(artists []*subsonic.ArtistID3) []*subsonic.ArtistID3 {
@@ -46,6 +62,17 @@ func (s *subsonicMediaProvider) IterateArtists(sortOrder string, filter mediapro
 			},
 			filter,
 		)
+	case ArtistSortRandom:
+		return s.baseArtistIterFromSimpleSortOrder(
+			func(artists []*subsonic.ArtistID3) []*subsonic.ArtistID3 {
+				newArtists := make([]*subsonic.ArtistID3, len(artists))
+				copy(newArtists, artists)
+				r := rand.New(rand.NewSource(time.Now().UnixNano()))
+				r.Shuffle(len(newArtists), func(i, j int) { newArtists[i], newArtists[j] = newArtists[j], newArtists[i] })
+				return newArtists
+			},
+			filter,
+		)
 	default:
 		log.Printf("Undefined artist sort order: %s", sortOrder)
 		return nil