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/src/api/admin/crawler/control.rs

@@ -24,6 +24,7 @@ use super::require_crawler;
 pub(super) fn routes() -> Router<AppState> {
     Router::new()
         .route("/admin/crawler/run", post(run_now))
+        .route("/admin/crawler/reconcile", post(reconcile_now))
         .route("/admin/crawler/browser/restart", post(restart_browser))
         .route("/admin/crawler/session", post(update_session))
         .route(
@@ -71,6 +72,45 @@ async fn run_now(
     Ok(Json(RunResponse { started: true }))
 }
 
+async fn reconcile_now(
+    State(state): State<AppState>,
+    admin: RequireAdmin,
+) -> AppResult<Json<RunResponse>> {
+    let c = require_crawler(&state)?;
+    let rp = c.reconcile_pass.as_ref().ok_or_else(|| {
+        AppError::ServiceUnavailable("no source configured (CRAWLER_START_URL unset)".into())
+    })?;
+    // Share `manual_pass_lock` with the metadata pass: reconcile's list walk
+    // and a metadata pass both contend for the single browser lease, so they
+    // must not run concurrently. A click while either is in flight gets 409.
+    let pass_guard = c
+        .manual_pass_lock
+        .clone()
+        .try_lock_owned()
+        .map_err(|_| AppError::Conflict("a metadata or reconcile pass is already running".into()))?;
+    let rp = std::sync::Arc::clone(rp);
+    // Fire-and-forget: the full list walk runs for minutes; progress streams
+    // over SSE (the Reconciling phase). The guard moves into the task so the
+    // lock releases only when the walk + enqueue finish.
+    tokio::spawn(async move {
+        let _pass_guard = pass_guard;
+        match rp.run().await {
+            Ok(stats) => tracing::info!(?stats, "manual reconcile pass complete"),
+            Err(e) => tracing::warn!(error = ?e, "manual reconcile pass failed"),
+        }
+    });
+    repo::admin_audit::insert(
+        &state.db,
+        admin.0.id,
+        "crawler_reconcile",
+        "crawler",
+        None,
+        json!({}),
+    )
+    .await?;
+    Ok(Json(RunResponse { started: true }))
+}
+
 #[derive(Debug, Serialize)]
 struct RestartResponse {
     ok: bool,