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/src/crawler/jobs.rs

@@ -104,6 +104,12 @@ pub async fn enqueue(pool: &PgPool, payload: &JobPayload) -> sqlx::Result<Enqueu
 ///
 /// `kind_filter` matches against `payload->>'kind'`; `None` means
 /// any kind.
+///
+/// Ties on `scheduled_at` (the common case: a cron batch enqueues
+/// everything with the same default `now()`) break by `created_at`, so
+/// jobs come off the queue in insertion order. The enqueue paths insert
+/// chapter-content jobs in ascending `chapters.number` order, so this
+/// tiebreaker is what propagates that intent through to dequeue.
 pub async fn lease(
     pool: &PgPool,
     kind_filter: Option<&str>,
@@ -118,7 +124,7 @@ pub async fn lease(
              WHERE (state = 'pending' OR (state = 'running' AND leased_until < now()))
                AND scheduled_at <= now()
                AND ($1::text IS NULL OR payload->>'kind' = $1)
-             ORDER BY scheduled_at
+             ORDER BY scheduled_at, created_at
              LIMIT $2
              FOR UPDATE SKIP LOCKED
         )

backend/src/crawler/pipeline.rs

@@ -429,8 +429,8 @@ pub async fn enqueue_bookmarked_pending(pool: &PgPool) -> anyhow::Result<Enqueue
                   AND cj.state = 'dead'
                   AND cj.updated_at > now() - ($1::bigint || ' days')::interval
            )
-         GROUP BY cs.source_id, c.id, cs.source_chapter_key, c.manga_id, c.created_at
-         ORDER BY c.manga_id, c.created_at ASC
+         GROUP BY cs.source_id, c.id, cs.source_chapter_key, c.manga_id, c.number, c.created_at
+         ORDER BY c.manga_id, c.number ASC, c.created_at ASC
         "#,
     )
     .bind(CHAPTER_DEAD_QUARANTINE_DAYS)
@@ -471,7 +471,7 @@ pub async fn enqueue_pending_for_manga(
 ) -> anyhow::Result<EnqueueSummary> {
     let rows: Vec<(String, Uuid, String)> = sqlx::query_as(
         r#"
-        SELECT DISTINCT cs.source_id, c.id AS chapter_id, cs.source_chapter_key
+        SELECT cs.source_id, c.id AS chapter_id, cs.source_chapter_key
           FROM chapters c
           JOIN chapter_sources cs ON cs.chapter_id = c.id
          WHERE c.manga_id = $1
@@ -484,7 +484,8 @@ pub async fn enqueue_pending_for_manga(
                   AND cj.state = 'dead'
                   AND cj.updated_at > now() - ($2::bigint || ' days')::interval
            )
-         ORDER BY cs.source_id, c.id
+         GROUP BY cs.source_id, c.id, cs.source_chapter_key, c.number, c.created_at
+         ORDER BY c.number ASC, c.created_at ASC, cs.source_id
         "#,
     )
     .bind(manga_id)