fix: the wanted-list tests set a track's MBID with its source, and find the missing-files link in its row (M502 #5520)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

web/src/routes/admin/missing-files/missing-files.test.ts

@@ -1,5 +1,5 @@
 import { afterEach, describe, expect, test, vi } from 'vitest';
-import { render, screen } from '@testing-library/svelte';
+import { render, screen, within } from '@testing-library/svelte';
 import { mockQuery } from '../../../test-utils/query';
 import type { AdminMissingResponse } from '#lib/api/types.js';
 
@@ -137,7 +137,9 @@ describe('admin missing files', () => {
     renderWith(withState);
     const line = text('reacquisition-state');
     expect(line).toMatch(/on the wanted list since 2d ago/i);
-    expect(screen.getByRole('link', { name: /wanted list/i }).getAttribute('href')).toBe(
+    expect(
+      within(screen.getByTestId('reacquisition-state')).getByRole('link', { name: /wanted list/i }).getAttribute('href')
+    ).toBe(
       '/admin/wanted?tab=missing'
     );
   });