bugfix: bookmark chapter links use chapter number, not UUID

The reader route is keyed on chapter number (URL `/manga/{id}/chapter/{n}`,
loaded via `Number(params.n)`), but the bookmarks list was building
hrefs from `chapter_id` (a UUID). Following any chapter bookmark
produced a NaN load on the reader page.

Fix at the API layer so every consumer of /me/bookmarks gets the
information without a follow-up round-trip per bookmark.

- domain::BookmarkSummary: new type, `Bookmark` plus
  `chapter_number: Option<i32>`. Populated by a LEFT JOIN on chapters
  so manga-level bookmarks come back with `chapter_number = null` and
  chapter-level ones get the value. `Bookmark` itself stays minimal
  for POST / DELETE responses.
- repo::bookmark::list_for_user returns Vec<BookmarkSummary>.
- api::bookmarks::list_me returns PagedResponse<BookmarkSummary>.
- Frontend `Bookmark` type carries an optional `chapter_number`.
- /bookmarks page builds `/manga/{manga_id}/chapter/{chapter_number}`
  for chapter bookmarks, falling back to the manga overview if the
  chapter has been deleted out from under the bookmark (chapter_id is
  ON DELETE SET NULL, so this is a real edge case).

New test asserts both branches of the JOIN: a chapter-level bookmark
comes back with the right chapter_number and page, a manga-level one
has a null chapter_number.

Lockstep version bump to 0.9.2.

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

backend/src/api/bookmarks.rs

@@ -12,7 +12,7 @@ use uuid::Uuid;
 use crate::api::pagination::PagedResponse;
 use crate::app::AppState;
 use crate::auth::extractor::CurrentUser;
-use crate::domain::Bookmark;
+use crate::domain::{Bookmark, BookmarkSummary};
 use crate::error::{AppError, AppResult};
 use crate::repo;
 
@@ -95,7 +95,7 @@ async fn list_me(
     State(state): State<AppState>,
     CurrentUser(user): CurrentUser,
     Query(params): Query<ListParams>,
-) -> AppResult<Json<PagedResponse<Bookmark>>> {
+) -> AppResult<Json<PagedResponse<BookmarkSummary>>> {
     let limit = params.limit.clamp(1, 200);
     let offset = params.offset.max(0);
     let items = repo::bookmark::list_for_user(&state.db, user.id, limit, offset).await?;

backend/src/domain/bookmark.rs

@@ -12,3 +12,19 @@ pub struct Bookmark {
     pub page: Option<i32>,
     pub created_at: DateTime<Utc>,
 }
+
+/// `Bookmark` enriched with the chapter's reader-facing number, so the
+/// frontend can build `/manga/{id}/chapter/{number}` links without an
+/// extra round-trip per bookmark. Populated by a LEFT JOIN; `null` for
+/// manga-level bookmarks or for chapter bookmarks whose chapter has
+/// since been deleted (`chapter_id` is `ON DELETE SET NULL`).
+#[derive(Debug, Clone, Serialize, FromRow)]
+pub struct BookmarkSummary {
+    pub id: Uuid,
+    pub user_id: Uuid,
+    pub manga_id: Uuid,
+    pub chapter_id: Option<Uuid>,
+    pub chapter_number: Option<i32>,
+    pub page: Option<i32>,
+    pub created_at: DateTime<Utc>,
+}

backend/src/domain/mod.rs

@@ -7,7 +7,7 @@ pub mod session;
 pub mod user;
 
 pub use api_token::ApiToken;
-pub use bookmark::Bookmark;
+pub use bookmark::{Bookmark, BookmarkSummary};
 pub use chapter::Chapter;
 pub use manga::Manga;
 pub use page::Page;

backend/src/repo/bookmark.rs

@@ -3,7 +3,7 @@
 use sqlx::PgPool;
 use uuid::Uuid;
 
-use crate::domain::Bookmark;
+use crate::domain::{Bookmark, BookmarkSummary};
 use crate::error::{AppError, AppResult};
 
 pub async fn create(
@@ -36,18 +36,31 @@ pub async fn create(
     }
 }
 
+/// Returns the user's bookmarks enriched with each chapter's number
+/// (LEFT JOINed; `chapter_number` is `null` for manga-level bookmarks
+/// or for chapter bookmarks whose chapter has since been deleted —
+/// `bookmarks.chapter_id` is `ON DELETE SET NULL`). The frontend uses
+/// the number to build reader URLs, which are keyed on number, not id.
 pub async fn list_for_user(
     pool: &PgPool,
     user_id: Uuid,
     limit: i64,
     offset: i64,
-) -> AppResult<Vec<Bookmark>> {
-    let rows = sqlx::query_as::<_, Bookmark>(
+) -> AppResult<Vec<BookmarkSummary>> {
+    let rows = sqlx::query_as::<_, BookmarkSummary>(
         r#"
-        SELECT id, user_id, manga_id, chapter_id, page, created_at
-        FROM bookmarks
-        WHERE user_id = $1
-        ORDER BY created_at DESC
+        SELECT
+            b.id,
+            b.user_id,
+            b.manga_id,
+            b.chapter_id,
+            c.number AS chapter_number,
+            b.page,
+            b.created_at
+        FROM bookmarks b
+        LEFT JOIN chapters c ON c.id = b.chapter_id
+        WHERE b.user_id = $1
+        ORDER BY b.created_at DESC
         LIMIT $2 OFFSET $3
         "#,
     )