fix(crawler): queue chapter content in ascending number order (0.51.1)

Both enqueue paths now order by chapters.number so the cron tick and the
bookmark hook insert jobs from chapter 1 upward instead of source-discovery
or random-UUID order. The lease query tiebreaks on created_at so jobs
sharing a batch's scheduled_at come off the queue in insertion order,
propagating the enqueue intent through to dequeue. Concurrent workers
and per-CDN latency can still drift actual completion order.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

backend/tests/crawler_daemon.rs

@@ -517,3 +517,132 @@ async fn enqueue_bookmarked_pending_resumes_after_quarantine_expires(pool: PgPoo
     );
 }
 
+/// Helper: insert a chapter with the given `number` and a non-dropped
+/// source row, returning the chapter id. Used by the ordering tests so
+/// the setup boilerplate doesn't drown the assertion.
+async fn insert_pending_chapter(
+    pool: &PgPool,
+    manga_id: Uuid,
+    number: i32,
+    source_chapter_key: &str,
+) -> Uuid {
+    let chapter_id: Uuid = sqlx::query_scalar(
+        "INSERT INTO chapters (manga_id, number, page_count) VALUES ($1, $2, 0) RETURNING id",
+    )
+    .bind(manga_id)
+    .bind(number)
+    .fetch_one(pool)
+    .await
+    .unwrap();
+    sqlx::query(
+        "INSERT INTO chapter_sources (source_id, source_chapter_key, chapter_id, source_url) \
+         VALUES ($1, $2, $3, $4)",
+    )
+    .bind("target")
+    .bind(source_chapter_key)
+    .bind(chapter_id)
+    .bind(format!("https://example.com/{source_chapter_key}"))
+    .execute(pool)
+    .await
+    .unwrap();
+    chapter_id
+}
+
+#[sqlx::test(migrations = "./migrations")]
+async fn enqueue_bookmarked_pending_queues_chapters_in_ascending_number_order(pool: PgPool) {
+    // Insert chapters with `number` values 3, 1, 2 in that insertion
+    // order — so `created_at` order (the previous tiebreaker) does NOT
+    // match number order. After enqueue + lease, the worker should see
+    // chapters 1, 2, 3 in that sequence.
+    let user_id: Uuid = sqlx::query_scalar(
+        "INSERT INTO users (username, password_hash) VALUES ($1, $2) RETURNING id",
+    )
+    .bind("alice")
+    .bind("not-a-real-hash")
+    .fetch_one(&pool)
+    .await
+    .unwrap();
+    let manga_id: Uuid = sqlx::query_scalar("INSERT INTO mangas (title) VALUES ($1) RETURNING id")
+        .bind("Test")
+        .fetch_one(&pool)
+        .await
+        .unwrap();
+    sqlx::query(
+        "INSERT INTO sources (id, name, base_url) VALUES ($1, $2, $3) ON CONFLICT DO NOTHING",
+    )
+    .bind("target")
+    .bind("Target")
+    .bind("https://example.com")
+    .execute(&pool)
+    .await
+    .unwrap();
+    let c3 = insert_pending_chapter(&pool, manga_id, 3, "ch3").await;
+    let c1 = insert_pending_chapter(&pool, manga_id, 1, "ch1").await;
+    let c2 = insert_pending_chapter(&pool, manga_id, 2, "ch2").await;
+    sqlx::query("INSERT INTO bookmarks (user_id, manga_id) VALUES ($1, $2)")
+        .bind(user_id)
+        .bind(manga_id)
+        .execute(&pool)
+        .await
+        .unwrap();
+
+    let summary = pipeline::enqueue_bookmarked_pending(&pool).await.unwrap();
+    assert_eq!(summary.inserted, 3);
+
+    let leases = jobs::lease(&pool, None, 10, std::time::Duration::from_secs(60))
+        .await
+        .unwrap();
+    let leased_chapter_ids: Vec<Uuid> = leases
+        .iter()
+        .map(|l| match &l.payload {
+            JobPayload::SyncChapterContent { chapter_id, .. } => *chapter_id,
+            other => panic!("unexpected payload kind: {other:?}"),
+        })
+        .collect();
+    assert_eq!(
+        leased_chapter_ids,
+        vec![c1, c2, c3],
+        "chapters must be leased in ascending chapter-number order, not insertion order"
+    );
+}
+
+#[sqlx::test(migrations = "./migrations")]
+async fn enqueue_pending_for_manga_queues_chapters_in_ascending_number_order(pool: PgPool) {
+    // Same scenario as above but exercising the bookmark-create hook path
+    // (`enqueue_pending_for_manga`) which has its own ORDER BY.
+    let manga_id: Uuid = sqlx::query_scalar("INSERT INTO mangas (title) VALUES ($1) RETURNING id")
+        .bind("Test")
+        .fetch_one(&pool)
+        .await
+        .unwrap();
+    sqlx::query(
+        "INSERT INTO sources (id, name, base_url) VALUES ($1, $2, $3) ON CONFLICT DO NOTHING",
+    )
+    .bind("target")
+    .bind("Target")
+    .bind("https://example.com")
+    .execute(&pool)
+    .await
+    .unwrap();
+    let c3 = insert_pending_chapter(&pool, manga_id, 3, "ch3").await;
+    let c1 = insert_pending_chapter(&pool, manga_id, 1, "ch1").await;
+    let c2 = insert_pending_chapter(&pool, manga_id, 2, "ch2").await;
+
+    let summary = pipeline::enqueue_pending_for_manga(&pool, manga_id)
+        .await
+        .unwrap();
+    assert_eq!(summary.inserted, 3);
+
+    let leases = jobs::lease(&pool, None, 10, std::time::Duration::from_secs(60))
+        .await
+        .unwrap();
+    let leased_chapter_ids: Vec<Uuid> = leases
+        .iter()
+        .map(|l| match &l.payload {
+            JobPayload::SyncChapterContent { chapter_id, .. } => *chapter_id,
+            other => panic!("unexpected payload kind: {other:?}"),
+        })
+        .collect();
+    assert_eq!(leased_chapter_ids, vec![c1, c2, c3]);
+}
+