feat(albums): "Artist → Year" album sort option (#1120)

* feat(albums): "Artist → Year" sort option

Adds a third album browse sort that groups albums by artist and orders each
artist's albums chronologically (oldest first, title as a same-year tiebreak)
— the double-sort requested in #1113. The local index sorts globally via
[{artist},{year},{name}]; the server fallback fetches by artist and applies the
year ordering per page (Subsonic has no compound sort).

* i18n(albums): Artist → Year sort label (9 locales)

* docs(changelog): add Artist → Year to the album sorting entry (#1120)

src/pages/Albums.tsx

@@ -354,6 +354,7 @@ export default function Albums() {
   const sortOptions: { value: SortType; label: string }[] = [
     { value: 'alphabeticalByName',   label: t('albums.sortByName') },
     { value: 'alphabeticalByArtist', label: t('albums.sortByArtist') },
+    { value: 'byArtistThenYear',     label: t('albums.sortByArtistYear') },
   ];
 
   return (