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/es.ts

@@ -774,6 +774,7 @@ export const esTranslation = {
     genreDistribution: 'Distribución de Géneros (Top 20)',
     loadMore: 'Cargar más',
     statArtists: 'Artistas',
+    statArtistsTooltip: 'Solo artistas de álbum — los artistas que aparecen únicamente como artistas de pista (featuring, invitado, etc.) sin álbum propio no se cuentan.',
     statAlbums: 'Álbumes',
     statSongs: 'Canciones',
     statGenres: 'Géneros',