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>

backend/tests/crawler_dead_jobs.rs

@@ -116,6 +116,57 @@ async fn list_dead_jobs_filters_by_title_search(pool: PgPool) {
     assert_eq!(items[0].manga_title.as_deref(), Some("One Piece"));
 }
 
+/// Insert a dead `sync_manga` job (no manga/chapter rows) — the reconcile
+/// "detail page gone" case.
+async fn insert_dead_sync_manga(pool: &PgPool, key: &str, title: &str) -> Uuid {
+    let id = Uuid::new_v4();
+    let payload = json!({
+        "kind": "sync_manga",
+        "source_id": "target",
+        "source_manga_key": key,
+        "url": format!("http://x/manga/{key}"),
+        "title": title,
+    });
+    sqlx::query(
+        "INSERT INTO crawler_jobs (id, payload, state, attempts, last_error) \
+         VALUES ($1, $2, 'dead', 5, 'broken-page body signature')",
+    )
+    .bind(id)
+    .bind(payload)
+    .execute(pool)
+    .await
+    .unwrap();
+    id
+}
+
+#[sqlx::test(migrations = "./migrations")]
+async fn dead_sync_manga_job_surfaces_payload_title_and_url(pool: PgPool) {
+    insert_dead_sync_manga(&pool, "gone-1", "Ghost Manga").await;
+
+    let (items, total) = crawler::list_dead_jobs(&pool, None, 50, 0).await.unwrap();
+    assert_eq!(total, 1);
+    let row = &items[0];
+    // No manga row exists → manga_title is None; the payload fields fill in.
+    assert_eq!(row.manga_title, None);
+    assert_eq!(row.payload_title.as_deref(), Some("Ghost Manga"));
+    assert_eq!(row.source_url.as_deref(), Some("http://x/manga/gone-1"));
+    assert_eq!(row.source_key.as_deref(), Some("gone-1"));
+    assert_eq!(row.kind, "sync_manga");
+    assert_eq!(row.last_error.as_deref(), Some("broken-page body signature"));
+}
+
+#[sqlx::test(migrations = "./migrations")]
+async fn dead_jobs_search_matches_payload_title(pool: PgPool) {
+    insert_dead_sync_manga(&pool, "gone-1", "Ghost Manga").await;
+    insert_dead_sync_manga(&pool, "gone-2", "Other Title").await;
+
+    let (items, total) = crawler::list_dead_jobs(&pool, Some("ghost"), 50, 0)
+        .await
+        .unwrap();
+    assert_eq!(total, 1);
+    assert_eq!(items[0].payload_title.as_deref(), Some("Ghost Manga"));
+}
+
 #[sqlx::test(migrations = "./migrations")]
 async fn requeue_all_resets_dead_jobs_to_pending(pool: PgPool) {
     let (_m, c1) = seed_chapter(&pool, "A", 1).await;