fix(library): show album cover art in the Albums grid

The album cards always fell back to the 💿 placeholder: the mapper dropped
the backend's `has_cover` and no album cover URL was ever built. Carry
`hasCover` through `RawAlbum`/`Album` and add `getAlbumCoverUrl` (GET
/albums/{id}/cover, token in the query like the track/stream URLs). The
Library Albums grid and the artist-detail discography now render real
covers, same source the album-detail page already used.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/features/library/LibraryPage.tsx

@@ -28,7 +28,7 @@ import {
 } from '../../store/selectors/localLibrary';
 import { setQueue } from '../../store/slices/queue';
 import type { Track, Album, Artist } from '../../api/types';
-import { getCoverUrl } from '../../api/endpoints/streaming';
+import { getCoverUrl, getAlbumCoverUrl } from '../../api/endpoints/streaming';
 import { formatDuration } from '../../lib/format';
 import { useDebounce } from 'use-debounce';
 
@@ -300,7 +300,12 @@ export function LibraryPage() {
 
 function AlbumCard({ album, onClick }: { album: Album; onClick: () => void }) {
   const { t } = useTranslation();
-  const artUrl = getCoverUrl(album.artUrl);
+  const token = useAppSelector((s) => s.auth.accessToken);
+  // The album record has no cover URL; build one from `hasCover` (served by
+  // GET /albums/{id}/cover, token in the query — <img> can't send a header).
+  const artUrl =
+    getCoverUrl(album.artUrl) ??
+    (token ? getAlbumCoverUrl(album.id, token, album.hasCover) : undefined);
   return (
     <Card
       onClick={onClick}