feat: bookmark create enqueues SyncChapterContent jobs (0.29.0)

After a successful bookmark insert, the create handler spawns a
detached tokio task that calls pipeline::enqueue_pending_for_manga
for every chapter of the manga where page_count = 0 and the source
row is not dropped. Bookmark create returns 201 immediately; enqueue
work happens in the background and its failure is logged without
surfacing to the user (the daily cron sweeps anything missed).

The Phase A dedup index handles re-bookmarks idempotently — deleting
and recreating a bookmark does not duplicate in-flight jobs — and the
Phase B worker pool drains them.

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

backend/src/api/bookmarks.rs

@@ -13,6 +13,7 @@ use uuid::Uuid;
 use crate::api::pagination::PagedResponse;
 use crate::app::AppState;
 use crate::auth::extractor::CurrentUser;
+use crate::crawler::pipeline;
 use crate::domain::{Bookmark, BookmarkSummary};
 use crate::error::{AppError, AppResult};
 use crate::repo;
@@ -86,6 +87,29 @@ async fn create(
         input.page,
     )
     .await?;
+
+    // Fire-and-forget: kick off content syncs for any pending chapters of
+    // the newly-bookmarked manga. The dedup index makes this idempotent
+    // across repeated bookmarks of the same manga; failure here must not
+    // surface to the user (the daily cron sweeps anything missed).
+    let pool = state.db.clone();
+    let manga_id = input.manga_id;
+    tokio::spawn(async move {
+        match pipeline::enqueue_pending_for_manga(&pool, manga_id).await {
+            Ok(summary) => tracing::info!(
+                %manga_id,
+                inserted = summary.inserted,
+                skipped = summary.skipped,
+                failed = summary.failed,
+                "bookmark hook: enqueued pending chapters"
+            ),
+            Err(e) => tracing::warn!(
+                %manga_id, error = ?e,
+                "bookmark hook: enqueue_pending_for_manga failed"
+            ),
+        }
+    });
+
     Ok((StatusCode::CREATED, Json(bookmark)))
 }