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>

frontend/src/lib/api/authors.ts

@@ -0,0 +1,56 @@
+import { request, type Page } from './client';
+import type { Manga } from './client';
+
+export type Author = {
+    id: string;
+    name: string;
+    created_at: string;
+};
+
+/** Returned by `GET /v1/authors/:id` — adds the count of attached mangas. */
+export type AuthorWithCount = Author & {
+    manga_count: number;
+};
+
+export type AuthorMangasPage = {
+    items: Manga[];
+    page: Page;
+};
+
+export type ListAuthorsOptions = {
+    search?: string;
+    limit?: number;
+    offset?: number;
+};
+
+export type ListAuthorMangasOptions = {
+    limit?: number;
+    offset?: number;
+};
+
+/** Autocomplete for author pickers. Server sorts by trigram similarity. */
+export async function listAuthors(opts: ListAuthorsOptions = {}): Promise<Author[]> {
+    const params = new URLSearchParams();
+    if (opts.search) params.set('search', opts.search);
+    if (opts.limit != null) params.set('limit', String(opts.limit));
+    if (opts.offset != null) params.set('offset', String(opts.offset));
+    const qs = params.toString();
+    return request<Author[]>(`/v1/authors${qs ? `?${qs}` : ''}`);
+}
+
+export async function getAuthor(id: string): Promise<AuthorWithCount> {
+    return request<AuthorWithCount>(`/v1/authors/${encodeURIComponent(id)}`);
+}
+
+export async function listAuthorMangas(
+    id: string,
+    opts: ListAuthorMangasOptions = {}
+): Promise<AuthorMangasPage> {
+    const params = new URLSearchParams();
+    if (opts.limit != null) params.set('limit', String(opts.limit));
+    if (opts.offset != null) params.set('offset', String(opts.offset));
+    const qs = params.toString();
+    return request<AuthorMangasPage>(
+        `/v1/authors/${encodeURIComponent(id)}/mangas${qs ? `?${qs}` : ''}`
+    );
+}