feat(crawler): reconcile pass to enqueue mangas missing from the DB (0.85.0)

The interleaved metadata pass misses mangas to list drift (a title slips a
pagination slot during the slow detail walk). Add a reconcile pass: a cheap,
full, list-only walk (refs only, no detail visit, no early stop) that
set-diffs the walked keys against manga_sources and enqueues the strictly-
missing ones as SyncManga jobs. A set-diff is immune to drift — a manga only
has to appear somewhere in the list.

- Build the previously-dead SyncManga worker by extending RealChapterDispatcher
  to run the shared pipeline::process_manga_ref (fetch → upsert → cover →
  chapters), refactored out of run_metadata_pass so both paths stay in lockstep.
  The crawl worker now leases both sync_chapter_content and sync_manga
  (jobs::lease_kinds); both serialize on the single exclusive browser.
- SyncManga payload carries url + title so the worker can rebuild the ref and
  the dead-jobs/history UI can label a missing manga that has no manga row yet.
- "Missing" = strict NOT EXISTS (dropped rows count as present). Re-enqueue is
  skipped when a pending/running/dead SyncManga job already exists, so a gone
  manga (detail 404 → retries → dead) is left dead and not retried.
- New POST /v1/admin/crawler/reconcile (fire-and-forget, shares
  manual_pass_lock) + "Reconcile missing" admin button + Reconciling status
  phase streamed over SSE.
- dead-jobs/history queries surface payload title/url/key; tables fall back to
  them for sync_manga rows; both searches match the payload title.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend/src/lib/api/admin.test.ts

@@ -23,6 +23,7 @@ import {
     getCrawlerStatus,
     crawlerStatusStreamUrl,
     runCrawlerPass,
+    reconcileCrawler,
     restartCrawlerBrowser,
     updateCrawlerSession,
     clearCrawlerSessionExpired,
@@ -479,6 +480,15 @@ describe('admin crawler api client', () => {
         expect(fetchSpy.mock.calls[0][0]).toMatch(/\/v1\/admin\/crawler\/run$/);
     });
 
+    it('reconcileCrawler POSTs /v1/admin/crawler/reconcile', async () => {
+        fetchSpy.mockResolvedValueOnce(ok({ started: true }));
+        const r = await reconcileCrawler();
+        expect(r.started).toBe(true);
+        const init = fetchSpy.mock.calls[0][1] as RequestInit;
+        expect(init.method).toBe('POST');
+        expect(fetchSpy.mock.calls[0][0]).toMatch(/\/v1\/admin\/crawler\/reconcile$/);
+    });
+
     it('restartCrawlerBrowser POSTs the restart endpoint', async () => {
         fetchSpy.mockResolvedValueOnce(ok({ ok: true, error: null }));
         const r = await restartCrawlerBrowser();