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/zh.ts

@@ -19,6 +19,7 @@ export const zhTranslation = {
     offlineLibrary: '离线音乐库',
     genres: '流派',
     playlists: '播放列表',
+    mostPlayed: '最常播放',
     radio: '网络电台',
     libraryScope: '资料库范围',
     allLibraries: '所有资料库',
@@ -773,6 +774,16 @@ export const zhTranslation = {
     metaSaved: '播放列表已更新',
     downloadZip: '下载 (ZIP)',
   },
+  mostPlayed: {
+    title: '最常播放',
+    topArtists: '热门艺术家',
+    topAlbums: '热门专辑',
+    plays: '播放 {{n}} 次',
+    sortMost: '最多播放在前',
+    sortLeast: '最少播放在前',
+    loadMore: '加载更多专辑',
+    noData: '暂无播放数据，开始聆听吧！',
+  },
   radio: {
     title: '网络电台',
     empty: '未配置任何电台。',