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/routes/admin/crawler/+page.svelte

@@ -16,6 +16,7 @@
         getCrawlerStatus,
         crawlerStatusStreamUrl,
         runCrawlerPass,
+        reconcileCrawler,
         restartCrawlerBrowser,
         updateCrawlerSession,
         clearCrawlerSessionExpired,
@@ -308,6 +309,13 @@
         });
     }
 
+    async function onReconcile() {
+        await withBusy('reconcile', async () => {
+            await reconcileCrawler();
+            notice = 'Reconcile started — walking the full list for missing mangas.';
+        });
+    }
+
     async function onConfirmRestart() {
         restartModalOpen = false;
         await withBusy('restart browser', async () => {
@@ -427,6 +435,7 @@
         {status}
         {busy}
         {onRunPass}
+        {onReconcile}
         onOpenRestart={() => (restartModalOpen = true)}
         onOpenSession={() => {
             sessionModalOpen = true;