feat(genres): local index genre browse with Subsonic fallback (#937)

* feat(genres): genre detail browse via local index with aligned counts

Move genre detail albums/play/shuffle onto the local library index with
Albums-style in-page scroll, session restore, and genre-scoped stash. Unify
genre album totals between the cloud and detail pages via
library_get_genre_album_counts, and fix grouped browse totals to count
distinct albums rather than matching tracks.

* perf(genres): local genre browse with scoped counts cache

Add dedicated Rust genre album pagination and indexes, slice-mode grid
loading, library-filter-aware counts, and a long-lived in-memory catalog
cache invalidated on sync so genre pages avoid repeated full-library SQL.

* fix(genres): restore scroll after album back; play hold-to-shuffle

Pin restore display count in refs so clearing the return stash no longer
reloads the genre grid mid-restore. Load the first SQL page only (60 rows),
use long-press on Play for shuffle, and add genre play tooltips.

* fix(genres): fall back to Subsonic byGenre when local index unavailable

Genre detail album grid now matches All Albums: try library_list_albums_by_genre
first, then getAlbumsByGenre when the index is off, not ready, or errors.

* docs: add CHANGELOG and credits for PR #937

src/api/subsonicGenres.ts

@@ -2,7 +2,9 @@ import { api, libraryFilterParams } from './subsonicClient';
 import type { SubsonicAlbum, SubsonicGenre, SubsonicSong } from './subsonicTypes';
 
 export async function getGenres(): Promise<SubsonicGenre[]> {
-  const data = await api<{ genres: { genre: SubsonicGenre | SubsonicGenre[] } }>('getGenres.view');
+  const data = await api<{ genres: { genre: SubsonicGenre | SubsonicGenre[] } }>('getGenres.view', {
+    ...libraryFilterParams(),
+  });
   const raw = data.genres?.genre;
   if (!raw) return [];
   return Array.isArray(raw) ? raw : [raw];