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/components/Sidebar.tsx

@@ -159,7 +159,7 @@ export default function Sidebar({
               <div className="nav-library-scope-text">
                 <span className="nav-library-scope-title">{t('sidebar.library')}</span>
                 {selectedFolderName ? (
-                  <span className="nav-library-scope-subtitle" title={selectedFolderName}>
+                  <span className="nav-library-scope-subtitle" data-tooltip={selectedFolderName} data-tooltip-pos="right">
                     {selectedFolderName}
                   </span>
                 ) : null}