fix(server,web): forward-fix CI lint + vitest failures

- gofmt -s on system.go, system_cron.go, api.go
- rename unused r → _ in 3 fetcher_test.go HTTP handlers
- TrackRow +queue test uses /add .* to queue/i (track-aware aria-label from #377)
- /library/artists page test mocks likes + tanstack-query (ArtistCard now embeds LikeButton)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

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

@@ -95,7 +95,7 @@ describe('TrackRow', () => {
 
   test('+ queue button calls enqueueTrack and does NOT trigger row play', async () => {
     render(TrackRow, { props: { tracks, index: 0 } });
-    await fireEvent.click(screen.getByRole('button', { name: /add to queue/i }));
+    await fireEvent.click(screen.getByRole('button', { name: /add .* to queue/i }));
     expect(enqueueTrack).toHaveBeenCalledWith(tracks[0]);
     expect(playQueue).not.toHaveBeenCalled();
   });

web/src/routes/library/artists/page.test.ts

@@ -20,7 +20,23 @@ vi.mock('$lib/api/queries', () => ({
   })
 }));
 vi.mock('$lib/api/client', () => ({ api: { get: vi.fn() } }));
-vi.mock('$lib/player/store.svelte', () => ({ playQueue: vi.fn() }));
+vi.mock('$lib/player/store.svelte', () => ({
+  playQueue: vi.fn(),
+  enqueueTracks: vi.fn()
+}));
+vi.mock('$lib/api/artists', () => ({
+  listArtistTracks: vi.fn().mockResolvedValue([])
+}));
+vi.mock('$lib/api/likes', () => ({
+  createLikedIdsQuery: () =>
+    readable({ data: { track_ids: [], album_ids: [], artist_ids: [] }, isPending: false, isError: false }),
+  likeEntity: vi.fn().mockResolvedValue(undefined),
+  unlikeEntity: vi.fn().mockResolvedValue(undefined)
+}));
+vi.mock('@tanstack/svelte-query', async (orig) => {
+  const actual = (await orig()) as Record<string, unknown>;
+  return { ...actual, useQueryClient: () => ({ invalidateQueries: vi.fn() }) };
+});
 
 import Page from './+page.svelte';