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/components/MangaCard.svelte

@@ -0,0 +1,107 @@
+<script lang="ts">
+    import { fileUrl } from '$lib/api/client';
+    import type { Manga } from '$lib/api/client';
+    import type { AuthorRef, GenreRef } from '$lib/api/mangas';
+    import BookImage from '@lucide/svelte/icons/book-image';
+
+    let {
+        manga,
+        authors = [],
+        genres = [],
+        testid
+    }: {
+        manga: Manga;
+        authors?: AuthorRef[];
+        genres?: GenreRef[];
+        testid?: string;
+    } = $props();
+</script>
+
+<li class="manga-card" data-testid={testid}>
+    <a href="/manga/{manga.id}" class="cover-link" aria-hidden="true" tabindex="-1">
+        {#if manga.cover_image_path}
+            <img
+                src={fileUrl(manga.cover_image_path)}
+                alt=""
+                class="cover"
+                loading="lazy"
+            />
+        {:else}
+            <div class="cover cover-placeholder">
+                <BookImage size={36} aria-hidden="true" />
+            </div>
+        {/if}
+    </a>
+    <div class="meta">
+        <a href="/manga/{manga.id}" class="title">{manga.title}</a>
+        {#if authors.length > 0}
+            <span class="author">{authors.map((a) => a.name).join(', ')}</span>
+        {/if}
+        {#if genres.length > 0}
+            <span class="genres">{genres.map((g) => g.name).join(' · ')}</span>
+        {/if}
+    </div>
+</li>
+
+<style>
+    .manga-card {
+        display: flex;
+        flex-direction: column;
+        gap: var(--space-2);
+        list-style: none;
+    }
+
+    .cover-link {
+        display: block;
+        line-height: 0;
+    }
+
+    .cover {
+        width: 100%;
+        aspect-ratio: 2 / 3;
+        object-fit: cover;
+        border-radius: var(--radius-md);
+        background: var(--surface);
+    }
+
+    .cover-placeholder {
+        display: flex;
+        align-items: center;
+        justify-content: center;
+        color: var(--text-muted);
+        user-select: none;
+    }
+
+    .meta {
+        display: flex;
+        flex-direction: column;
+        min-width: 0;
+        gap: var(--space-1);
+    }
+
+    .title {
+        font-weight: var(--weight-semibold);
+        font-size: var(--font-sm);
+        line-height: var(--leading-tight);
+        color: var(--text);
+        overflow: hidden;
+        display: -webkit-box;
+        -webkit-line-clamp: 2;
+        line-clamp: 2;
+        -webkit-box-orient: vertical;
+    }
+
+    .title:hover {
+        color: var(--primary);
+        text-decoration: none;
+    }
+
+    .author,
+    .genres {
+        color: var(--text-muted);
+        font-size: var(--font-xs);
+        white-space: nowrap;
+        overflow: hidden;
+        text-overflow: ellipsis;
+    }
+</style>