misc: Migrate Artists page to GridView

Remove custom page implementation for Artists, and instead rely on the
generic `GridView` approach. This also simplifies adding new
sorting/filtering options as next improvements.

The new `ArtistFilter` is a dummy implementation without any real
filters at the moment.

Also, the `go-jellyfin` upgrade is needed to correctly display the album
count for each artist.

ui/widgets/gridview.go

@@ -2,6 +2,7 @@ package widgets
 
 import (
 	"context"
+	"fmt"
 	"math"
 	"sync"
 
@@ -65,6 +66,30 @@ func NewGridViewAlbumIterator(iter mediaprovider.AlbumIterator) GridViewIterator
 	return gridViewAlbumIterator{iter: NewBatchingIterator(iter)}
 }
 
+type gridViewArtistIterator struct {
+	iter BatchingIterator[mediaprovider.Artist]
+}
+
+func (g gridViewArtistIterator) NextN(n int) []GridViewItemModel {
+	artists := g.iter.NextN(n)
+	return sharedutil.MapSlice(artists, func(ar *mediaprovider.Artist) GridViewItemModel {
+		albumsLabel := "albums"
+		if ar.AlbumCount == 1 {
+			albumsLabel = "album"
+		}
+		return GridViewItemModel{
+			Name:       ar.Name,
+			ID:         ar.ID,
+			CoverArtID: ar.CoverArtID,
+			Secondary:  []string{fmt.Sprintf("%d %s", ar.AlbumCount, albumsLabel)},
+		}
+	})
+}
+
+func NewGridViewArtistIterator(iter mediaprovider.ArtistIterator) GridViewIterator {
+	return gridViewArtistIterator{iter: NewBatchingIterator(iter)}
+}
+
 type GridView struct {
 	widget.BaseWidget