feat(web): add home/albums/artists API clients for M6a

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

web/src/lib/api/artists.test.ts

@@ -0,0 +1,23 @@
+import { afterEach, describe, expect, test, vi } from 'vitest';
+
+vi.mock('./client', () => ({
+  api: { get: vi.fn() }
+}));
+
+import { listArtistTracks } from './artists';
+import { qk } from './queries';
+import { api } from './client';
+
+afterEach(() => vi.clearAllMocks());
+
+describe('artists client', () => {
+  test('listArtistTracks hits /api/artists/:id/tracks', async () => {
+    (api.get as ReturnType<typeof vi.fn>).mockResolvedValueOnce([]);
+    await listArtistTracks('art-1');
+    expect(api.get).toHaveBeenCalledWith('/api/artists/art-1/tracks');
+  });
+
+  test('qk.artistTracks key includes the artist id', () => {
+    expect(qk.artistTracks('art-1')).toEqual(['artistTracks', 'art-1']);
+  });
+});