feat(web/m7-353): admin cover-refetch UI (per-album + bulk)

Adds cover_art_source to AlbumRef, two admin API helpers (refetchAlbumCover,
refetchMissingCovers), a per-album retry button gated on is_admin in the album
detail page, and a bulk-refetch section in the admin overview.

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

web/src/lib/api/admin.covers.test.ts

@@ -0,0 +1,33 @@
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+
+vi.mock('./client', () => ({
+  api: {
+    get: vi.fn(),
+    post: vi.fn(),
+    put: vi.fn(),
+    del: vi.fn()
+  }
+}));
+
+import { refetchAlbumCover, refetchMissingCovers } from './admin';
+import { api } from './client';
+
+describe('admin covers API', () => {
+  beforeEach(() => vi.clearAllMocks());
+
+  it('refetchAlbumCover POSTs to the correct path', async () => {
+    (api.post as unknown as ReturnType<typeof vi.fn>).mockResolvedValueOnce({
+      album_id: 'a1', cover_art_path: '/x.jpg', cover_art_source: 'mbcaa'
+    });
+    const got = await refetchAlbumCover('a1');
+    expect(api.post).toHaveBeenCalledWith('/api/admin/albums/a1/cover/refetch', {});
+    expect(got.cover_art_source).toBe('mbcaa');
+  });
+
+  it('refetchMissingCovers POSTs to the bulk endpoint', async () => {
+    (api.post as unknown as ReturnType<typeof vi.fn>).mockResolvedValueOnce({ queued: 7 });
+    const got = await refetchMissingCovers();
+    expect(api.post).toHaveBeenCalledWith('/api/admin/covers/refetch-missing', {});
+    expect(got.queued).toBe(7);
+  });
+});

web/src/lib/api/admin.ts

@@ -161,3 +161,23 @@ export function createQuarantineActionsQuery(limit: number = 50) {
     staleTime: 60_000
   });
 }
+
+// Admin cover art ---------------------------------------------------------
+
+export type RefetchAlbumCoverResponse = {
+  album_id: string;
+  cover_art_path: string | null;
+  cover_art_source: string | null;
+};
+
+export async function refetchAlbumCover(albumId: string): Promise<RefetchAlbumCoverResponse> {
+  return api.post<RefetchAlbumCoverResponse>(`/api/admin/albums/${albumId}/cover/refetch`, {});
+}
+
+export type RefetchMissingResponse = {
+  queued: number;
+};
+
+export async function refetchMissingCovers(): Promise<RefetchMissingResponse> {
+  return api.post<RefetchMissingResponse>('/api/admin/covers/refetch-missing', {});
+}

web/src/lib/api/types.ts

@@ -27,6 +27,7 @@ export type AlbumRef = {
   track_count: number;
   duration_sec: number;
   cover_url: string;
+  cover_art_source: string | null;
 };
 
 export type TrackRef = {