fix(library): multi-genre local index with track_genre and backfill (#1059)

* fix(library): multi-genre local index with track_genre and backfill

Restore atomic genre browse, filters, and counts via track_genre:
OpenSubsonic genres[] first with Navidrome-default split fallback, sync
write path, read-path query switches, blocking startup backfill with
progress, and v12 repair migration for DBs that recorded legacy 002–011.
TS fallback adds genreTagsFor and migration gate i18n across locales.

* fix(library): address multi-genre review — robust TS genres and scope join

genreTagsFor routes raw genres through parseItemGenres (single-object
Subsonic quirk and bare strings). Library-scoped genre browse/counts join
track for raw_json library_id fallback. Statistics keeps empty-genre bucket.

* docs: CHANGELOG and credits for multi-genre local index (PR #1059)

* docs(changelog): credit HiveMind on Discord for multi-genre report (PR #1059)

src/api/library.ts

@@ -892,3 +892,24 @@ export function subscribeLibrarySyncIdle(
     handler(payload),
   );
 }
+
+// ── Genre tags startup backfill (multi-genre local index) ───────────────
+
+export interface GenreTagsInspectDto {
+  needed: boolean;
+  totalTracks: number;
+  doneTracks: number;
+}
+
+export interface GenreTagsProgressEvent {
+  done: number;
+  total: number;
+}
+
+export function libraryGenreTagsInspect(): Promise<GenreTagsInspectDto> {
+  return invoke<GenreTagsInspectDto>('library_genre_tags_inspect');
+}
+
+export function libraryGenreTagsRun(): Promise<void> {
+  return invoke<void>('library_genre_tags_run');
+}