feat(web): add likes TanStack Query helpers + mutations

createLikedIdsQuery is the single source for heart-button state across
the app (track_ids/album_ids/artist_ids Sets). likeEntity / unlikeEntity
do optimistic setQueryData updates with rollback on error. Per-entity
infinite queries back the /library/liked sections.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

web/src/lib/api/queries.ts

@@ -15,6 +15,10 @@ export const qk = {
   searchArtists: (q: string) => ['searchArtists', { q }] as const,
   searchAlbums:  (q: string) => ['searchAlbums',  { q }] as const,
   searchTracks:  (q: string) => ['searchTracks',  { q }] as const,
+  likedIds:      ()          => ['likedIds'] as const,
+  likedTracks:   ()          => ['likedTracks'] as const,
+  likedAlbums:   ()          => ['likedAlbums'] as const,
+  likedArtists:  ()          => ['likedArtists'] as const,
 };
 
 export function createArtistsQuery(sort: ArtistSort) {