fix(favorites): show artist name in filter label, not Subsonic ID (#736)

Clicking a card under Top Artists by Favorites set the artist filter
to the artist's Subsonic ID, and the "Showing X of Y" label
interpolated that ID into the `{{artist}}` placeholder — so the user
saw a GUID like "OjdsOiMQ6ve5rZWPj2ePFc" instead of "Toto".

Look the name up from `topFavoriteArtists` (already on the page,
each entry carries `{id, name}`), and pass it to the header. The ID
filter itself is unchanged — the song-filtering hook still matches on
`artistId` / `artist` / `albumArtist`.

Reported by zunoz on Discord.

src/pages/Favorites.tsx

@@ -114,6 +114,11 @@ export default function Favorites() {
     selectedArtist, selectedGenres, yearRange, ratings,
   });
 
+  const selectedArtistName = useMemo(
+    () => selectedArtist ? topFavoriteArtists.find(a => a.id === selectedArtist)?.name ?? null : null,
+    [selectedArtist, topFavoriteArtists],
+  );
+
   const { toggleSelect } = useFavoritesSelection(songs, inSelectMode, tracklistRef);
 
 
@@ -174,6 +179,7 @@ export default function Favorites() {
                 visibleSongs={visibleSongs}
                 songs={songs}
                 selectedArtist={selectedArtist}
+                selectedArtistName={selectedArtistName}
                 setSelectedArtist={setSelectedArtist}
                 selectedGenres={selectedGenres}
                 setSelectedGenres={setSelectedGenres}