fix: v1.26.1 — hero/album/playlist background flickering

Background of Hero carousel, Album Detail and Playlist Detail was
flickering for up to 20 seconds on first visit. useCachedUrl with
fallbackToFetch=true returned the raw server URL immediately, causing
a double render — once with the HTTP URL and again when the blob was
ready. Fixed by passing fallbackToFetch=false in all three locations.

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

src/pages/AlbumDetail.tsx

@@ -234,7 +234,7 @@ const handleEnqueueAll = () => {
   // Hooks must be called unconditionally — derive from nullable album state
   const coverUrl = album?.album.coverArt ? buildCoverArtUrl(album.album.coverArt, 400) : '';
   const coverKey = album?.album.coverArt ? coverArtCacheKey(album.album.coverArt, 400) : '';
-  const resolvedCoverUrl = useCachedUrl(coverUrl, coverKey);
+  const resolvedCoverUrl = useCachedUrl(coverUrl, coverKey, false);
 
   if (loading) return <div className="loading-center"><div className="spinner" /></div>;
   if (!album) return <div className="empty-state">{t('albumDetail.notFound')}</div>;

src/pages/PlaylistDetail.tsx

@@ -136,7 +136,7 @@ export default function PlaylistDetail() {
 
   const bgFetchUrl = useMemo(() => buildCoverArtUrl(coverQuad[0] ?? '', 300), [coverQuad]);
   const bgCacheKey = useMemo(() => coverArtCacheKey(coverQuad[0] ?? '', 300), [coverQuad]);
-  const resolvedBgUrl = useCachedUrl(bgFetchUrl, bgCacheKey);
+  const resolvedBgUrl = useCachedUrl(bgFetchUrl, bgCacheKey, false);
 
   // Song search
   const [searchOpen, setSearchOpen] = useState(false);