fix(pr-review): address review findings for music folder filter

- Sidebar.tsx: title={} → data-tooltip + data-tooltip-pos="right" on
  scope subtitle (CLAUDE.md rule: never use native title= for tooltips)

- authStore.ts: merge two set() calls in setMusicFolders into one atomic
  update — avoids double render on folder list arrival

- locales (all 7): remove dead libraryScopeHint key (defined but never
  rendered in any component)

- Genres.tsx: remove musicLibraryFilterVersion from effect deps —
  getGenres is intentionally not folder-scoped, re-fetching on filter
  change was a no-op waste

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

src/locales/zh.ts

@@ -24,7 +24,6 @@ export const zhTranslation = {
     playlists: '播放列表',
     radio: '网络电台',
     libraryScope: '资料库范围',
-    libraryScopeHint: '浏览整个服务器目录或仅单个媒体文件夹。',
     allLibraries: '所有资料库',
   },
   home: {