feat(server/web/coverart): manual Re-search missing art button

POST /api/admin/cover-sources/research bumps cover_art_sources_meta.
current_version unconditionally; the next enrichment pass re-eligibles
every 'none' row. Existing positively-sourced rows are not affected —
the version-mismatch eligibility rule only kicks in for 'none'.

Admin Cover Art panel gains a "Re-search missing art" button that
calls the endpoint and shows a confirmation toast. Operator's escape
hatch when:

- They've added a Last.fm key and want to retry failed rows
  immediately rather than waiting for the next scheduled scan.
- An upstream provider's catalog has updated (e.g. Deezer added a
  back-catalog import).
- They want to verify a fix end-to-end before the next scheduled
  scan fires.

SettingsService.BumpVersion (the unconditional version of T5's
BumpVersionIfProvidersChanged) is the single-call DB writer; both
endpoints route through it.

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

web/src/lib/api/admin.research-art.test.ts

@@ -0,0 +1,19 @@
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+import { researchMissingArt } from './admin';
+
+vi.mock('./client', () => ({
+  api: { get: vi.fn(), post: vi.fn(), patch: vi.fn() }
+}));
+
+import { api } from './client';
+
+describe('admin research missing art API', () => {
+  beforeEach(() => vi.clearAllMocks());
+
+  it('researchMissingArt POSTs the correct path and returns version', async () => {
+    (api.post as unknown as ReturnType<typeof vi.fn>).mockResolvedValueOnce({ version: 7 });
+    const got = await researchMissingArt();
+    expect(api.post).toHaveBeenCalledWith('/api/admin/cover-sources/research', {});
+    expect(got.version).toBe(7);
+  });
+});

web/src/lib/api/admin.ts

@@ -320,6 +320,17 @@ export async function testCoverProvider(id: string): Promise<TestCoverProviderRe
   return api.post<TestCoverProviderResponse>(`/api/admin/cover-sources/${id}/test`, {});
 }
 
+// Re-search missing art --------------------------------------------------
+
+export type ResearchMissingArtResponse = { version: number };
+
+// Bumps cover_art_sources_meta.current_version. Every 'none' row becomes
+// eligible for retry against the current provider chain on the next
+// enrichment pass. Existing positively-sourced rows are not affected.
+export async function researchMissingArt(): Promise<ResearchMissingArtResponse> {
+  return api.post<ResearchMissingArtResponse>('/api/admin/cover-sources/research', {});
+}
+
 // Settings rarely change in operator time. 60s staleTime; refetches
 // on window focus + after any mutation rather than polling.
 export function createCoverProvidersQuery() {

web/src/routes/admin/+page.svelte

@@ -19,6 +19,7 @@
     deleteQuarantineViaLidarr,
     refetchMissingCovers,
     triggerScan,
+    researchMissingArt,
     type ScanSchedule,
     type ScanScheduleMode
   } from '$lib/api/admin';
@@ -315,6 +316,21 @@
   let bulkBusy = $state(false);
   let bulkResult = $state<string | null>(null);
 
+  // ---- Re-search missing art ----
+  let researchSaving = $state(false);
+
+  async function onResearchMissingArt() {
+    researchSaving = true;
+    try {
+      await researchMissingArt();
+      showToast('All previously-failed art will be re-attempted on the next scan.');
+    } catch (e) {
+      showToast(`Re-search failed: ${(e as { code?: string })?.code ?? 'unknown'}`);
+    } finally {
+      researchSaving = false;
+    }
+  }
+
   async function onBulkRefetch() {
     if (bulkBusy) return;
     bulkBusy = true;
@@ -603,6 +619,14 @@
       >
         {bulkBusy ? 'Queueing…' : 'Refetch missing covers'}
       </button>
+      <button
+        type="button"
+        onclick={onResearchMissingArt}
+        disabled={researchSaving}
+        class="rounded-md border border-border px-3 py-1.5 text-sm text-text-secondary hover:bg-surface-hover hover:text-text-primary disabled:opacity-50"
+      >
+        {researchSaving ? 'Bumping…' : 'Re-search missing art'}
+      </button>
 
       {#if coverage}
         {#if coverage.total === 0}

web/src/routes/admin/admin.test.ts

@@ -42,6 +42,7 @@ vi.mock('$lib/api/admin', async () => {
     deleteQuarantineViaLidarr: vi.fn().mockResolvedValue({}),
     triggerScan: vi.fn().mockResolvedValue({}),
     refetchMissingCovers: vi.fn().mockResolvedValue({ queued: 0 }),
+    researchMissingArt: vi.fn().mockResolvedValue({ version: 1 }),
     createScanScheduleQuery: vi.fn(() =>
       readable({
         data: {
@@ -111,7 +112,8 @@ import {
   rejectRequest,
   resolveQuarantine,
   deleteQuarantineFile,
-  deleteQuarantineViaLidarr
+  deleteQuarantineViaLidarr,
+  researchMissingArt
 } from '$lib/api/admin';
 import OverviewPage from './+page.svelte';
 
@@ -264,6 +266,15 @@ describe('admin Overview page', () => {
     expect(select.value).toBe('off');
   });
 
+  test('renders Re-search missing art button and invokes on click', async () => {
+    setupOverview();
+    render(OverviewPage);
+    const btn = screen.getByRole('button', { name: /re-search missing art/i });
+    expect(btn).toBeInTheDocument();
+    await fireEvent.click(btn);
+    expect(researchMissingArt).toHaveBeenCalled();
+  });
+
   test('Library scan card shows Processing badge when library tally is populated and in-flight', async () => {
     const { readable } = await import('svelte/store');
     (createScanStatusQuery as ReturnType<typeof vi.fn>).mockReturnValueOnce(