bugfix: /bookmarks renders manga title and cover

The bookmarks list was rendering "Manga bookmark <date>" with no
indication of which manga the bookmark referred to. The data is
already in the DB — the list query just wasn't pulling it.

Backend:
- BookmarkSummary gains manga_title (String) and
  manga_cover_image_path (Option<String>). Populated by an INNER JOIN
  on `mangas` in `repo::bookmark::list_for_user`. The JOIN is INNER
  because `bookmarks.manga_id` has ON DELETE CASCADE, so a bookmark
  cannot outlive its manga. Chapter LEFT JOIN unchanged.
- The existing list_me_enriches_chapter_bookmarks_with_chapter_number
  test now also asserts manga_title is populated for both chapter-
  and manga-level bookmarks, and that manga_cover_image_path is null
  when no cover was uploaded.

Frontend:
- Bookmark type carries optional manga_title and
  manga_cover_image_path (optional because POST /bookmarks returns
  the bare Bookmark, not the enriched summary).
- /bookmarks page redesigned as a grid: cover thumbnail (64×96 with
  a placeholder when no cover) on the left, then the manga title (as
  the primary link), then either "Chapter N — page M" linked to the
  reader, "(chapter removed)" for orphan chapter bookmarks, or
  "Whole manga" for manga-level bookmarks. Bookmark date moves to a
  subdued footer.
- E2E fixtures track the enriched shape returned by the list endpoint
  (vs. the bare Bookmark returned by POST). The toggle test now
  asserts the manga title appears on the bookmarks card after the
  bookmark is created.

Also: tighten .gitignore. `/data` only catches the compose volume
root; the dev backend writes to `/backend/data` (default STORAGE_DIR
is `./data/storage` relative to backend cwd), so local uploads were
showing as untracked. Adding `/backend/data` keeps test uploads out
of the index.

Lockstep version bump to 0.11.1.

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

backend/tests/api_bookmarks.rs

@@ -402,6 +402,11 @@ async fn list_me_enriches_chapter_bookmarks_with_chapter_number(pool: PgPool) {
         .expect("chapter-level bookmark present");
     assert_eq!(chapter_bookmark["chapter_number"], 7);
     assert_eq!(chapter_bookmark["page"], 4);
+    // Manga title is JOINed in too so the /bookmarks page can render
+    // a real card instead of "Manga bookmark".
+    assert_eq!(chapter_bookmark["manga_title"], "Berserk");
+    // No cover was uploaded for the seeded manga — null is correct.
+    assert!(chapter_bookmark["manga_cover_image_path"].is_null());
 
     let manga_bookmark = items
         .iter()
@@ -411,6 +416,7 @@ async fn list_me_enriches_chapter_bookmarks_with_chapter_number(pool: PgPool) {
         manga_bookmark["chapter_number"].is_null(),
         "manga-level bookmark must have a null chapter_number"
     );
+    assert_eq!(manga_bookmark["manga_title"], "Berserk");
 }
 
 #[sqlx::test(migrations = "./migrations")]