feat: author pages with /authors/:id route (0.16.0)

- `GET /v1/authors/:id` returns `AuthorWithCount` (id, name, manga_count).
- `GET /v1/authors/:id/mangas` paged works by that author.
- `GET /v1/authors?search=` autocomplete (already used by Phase 1 forms;
  now formally exposed).
- New `/authors/:id` page on the frontend; author chips on the manga
  detail page (added in Phase 1) now link to a real page.
- Extracts `lib/components/MangaCard.svelte` — already used by the home
  page, ready for the collection page in Phase 3.

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

backend/Cargo.lock

@@ -1033,7 +1033,7 @@ checksum = "5e5032e24019045c762d3c0f28f5b6b8bbf38563a65908389bf7978758920897"
 
 [[package]]
 name = "mangalord"
-version = "0.15.0"
+version = "0.16.0"
 dependencies = [
  "anyhow",
  "argon2",