feat(most-played): add dedicated Most Played page (#86)

New sidebar item (TrendingUp icon, /most-played route) with:

- Top Artists section: derived by grouping frequent albums by artistId
  and summing playCount — no extra API calls needed. Shows up to 10
  artists as a responsive grid with avatar, rank and total play count.
- Top Albums section: paginated list using getAlbumList('frequent'),
  50 albums per batch with a "Load more" button. Each row shows rank,
  cover thumbnail (44px), album name, artist (navigates to artist
  page), year and play count.
- Sort toggle (most plays first / fewest plays first).

Also adds playCount?: number to SubsonicAlbum — Navidrome returns this
field in getAlbumList2?type=frequent but it was missing from the type.

Closes #86

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/locales/en.ts

@@ -20,6 +20,7 @@ export const enTranslation = {
     offlineLibrary: 'Offline Library',
     genres: 'Genres',
     playlists: 'Playlists',
+    mostPlayed: 'Most Played',
     radio: 'Internet Radio',
     libraryScope: 'Library scope',
     allLibraries: 'All libraries',
@@ -778,6 +779,16 @@ export const enTranslation = {
     metaSaved: 'Playlist updated',
     downloadZip: 'Download (ZIP)',
   },
+  mostPlayed: {
+    title: 'Most Played',
+    topArtists: 'Top Artists',
+    topAlbums: 'Top Albums',
+    plays: '{{n}} plays',
+    sortMost: 'Most plays first',
+    sortLeast: 'Fewest plays first',
+    loadMore: 'Load more albums',
+    noData: 'No play data yet. Start listening!',
+  },
   radio: {
     title: 'Internet Radio',
     empty: 'No radio stations configured.',