fix(statistics): accurate counts for large libraries + album-artist tooltip

Remove the 10-page cap in fetchStatisticsLibraryAggregates — the loop now runs until
the server returns a partial page, so albums/songs/playtime reflect the full library
regardless of size (previously capped at 5,000 albums). Switched sort type from
'newest' to 'alphabeticalByName' for a stable pagination order.

Add a tooltip on the Artists stat card explaining it shows album artists only (Subsonic
API limitation — track-level featured/guest artists without their own album are not
included). Tooltip added in all 8 locales. Labels with a tooltip get a dotted underline
and cursor:help as visual hint.

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

src/locales/ru.ts

@@ -834,6 +834,7 @@ export const ruTranslation = {
     genreDistribution: 'Жанры (топ-20)',
     loadMore: 'Ещё',
     statArtists: 'Исполнители',
+    statArtistsTooltip: 'Только исполнители альбомов — артисты, присутствующие лишь в треках (фичеринг, гость и т. д.) без собственного альбома, не учитываются.',
     statAlbums: 'Альбомы',
     statSongs: 'Треки',
     statGenres: 'Жанры',