Heart appears on every entity rendering surface. ArtistRow restructured
to a <div> with the link as a positioned overlay so the heart button
can nest without invalid <button>-in-<a> markup. Shell nav grows a
'Liked' entry pointing at /library/liked.
Wraps the existing link in a relative container; adds an absolutely
positioned + button. On click stops propagation, fetches /api/albums/:id
once, and feeds tracks into enqueueTracks.
bvandeusen