feat(web): wire LikeButton into TrackRow, AlbumCard, ArtistRow, PlayerBar

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.

web/src/lib/components/ArtistRow.test.ts

@@ -1,8 +1,24 @@
-import { describe, expect, test } from 'vitest';
+import { describe, expect, test, vi } from 'vitest';
 import { render, screen } from '@testing-library/svelte';
+import { readable } from 'svelte/store';
 import ArtistRow from './ArtistRow.svelte';
 import type { ArtistRef } from '$lib/api/types';
 
+vi.mock('$lib/api/likes', () => ({
+  createLikedIdsQuery: () => readable({
+    data: { track_ids: [], album_ids: [], artist_ids: [] },
+    isPending: false,
+    isError: false
+  }),
+  likeEntity: vi.fn(),
+  unlikeEntity: vi.fn()
+}));
+
+vi.mock('@tanstack/svelte-query', async (orig) => {
+  const actual = (await orig()) as Record<string, unknown>;
+  return { ...actual, useQueryClient: () => ({}) };
+});
+
 const artist: ArtistRef = { id: 'abc', name: 'alice', album_count: 12 };
 
 describe('ArtistRow', () => {
@@ -11,14 +27,14 @@ describe('ArtistRow', () => {
 
     const link = screen.getByRole('link');
     expect(link).toHaveAttribute('href', '/artists/abc');
-    expect(link).toHaveTextContent('alice');
-    expect(link).toHaveTextContent('12 albums');
-    expect(link).toHaveTextContent('A'); // initial letter
+    expect(screen.getByText('alice')).toBeInTheDocument();
+    expect(screen.getByText('12 albums')).toBeInTheDocument();
+    expect(screen.getByText('A')).toBeInTheDocument();
   });
 
   test('singular "1 album" when album_count is 1', () => {
     render(ArtistRow, { props: { artist: { ...artist, album_count: 1 } } });
-    expect(screen.getByRole('link')).toHaveTextContent('1 album');
+    expect(screen.getByText('1 album')).toBeInTheDocument();
   });
 
   test('empty name still renders a safe initial', () => {