refactor(web): sweep 24 test files to use makeTrack/makeTracks fixtures (#375)

Replaces inline TrackRef literal redefinitions with calls to the
test-utils helper. Tests that asserted on default field values
(e.g. track titles, artist names rendered in the DOM) keep explicit
overrides; tests that only need a stub for shape now use makeTrack()
with no overrides.

PlaylistCard.test.ts, PlaylistTrackRow.test.ts, and playlist.test.ts
SKIPPED — they use PlaylistTrack (with track_id/added_at), not TrackRef.
ArtistCard.svelte and +page.svelte route files (matched by initial grep)
SKIPPED — live code, not test files.

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

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

@@ -1,7 +1,7 @@
 import { afterEach, describe, expect, test, vi } from 'vitest';
 import { render, screen, fireEvent } from '@testing-library/svelte';
 import FlagPopover from './FlagPopover.svelte';
-import type { TrackRef } from '$lib/api/types';
+import { makeTrack } from '$test-utils/fixtures/track';
 
 const invalidateMock = vi.fn();
 vi.mock('@tanstack/svelte-query', async (orig) => {
@@ -18,16 +18,7 @@ vi.mock('$lib/api/quarantine', () => ({
 
 import { flagTrack } from '$lib/api/quarantine';
 
-const track: TrackRef = {
-  id: 't1',
-  title: 'Roygbiv',
-  album_id: 'a1',
-  album_title: 'Geogaddi',
-  artist_id: 'ar1',
-  artist_name: 'Boards of Canada',
-  duration_sec: 240,
-  stream_url: '/api/tracks/t1/stream'
-};
+const track = makeTrack();
 
 afterEach(() => vi.clearAllMocks());