feat: manga collections (0.17.0)

User-owned named lists of mangas with an add-to-collection modal on
the manga page and dedicated /collections and /collections/:id pages.

- Schema (0010): `collections` (per-user case-insensitive name
  uniqueness) + `collection_mangas` join with cascade FKs.
- Endpoints: full CRUD on `/v1/collections`, idempotent add/remove
  for `/v1/collections/:id/mangas`, and `/v1/mangas/:id/my-collections`
  for the modal's pre-checked state. Owner-mismatch surfaces as 404
  (not 403) so the API doesn't disclose collection existence to
  non-owners; the frontend funnels 401 to /login. Three-state PATCH
  via a new shared `domain::patch::Patch<T>` lets clients distinguish
  "leave alone", "clear", and "set" for description.
- Frontend: reusable `Modal` component (focus trap, opt-in
  backdrop close, ESC) and `AddToCollectionModal` with optimistic
  toggling that's race-safe under fast clicks. /collections page
  renders cover-collage cards; /collections/:id is editable with
  per-card remove. Top nav gets a Collections link.

155 backend tests (incl. 21 collection tests covering ownership,
idempotence, sample-cover enrichment, three-state PATCH, FK race);
88 frontend tests; svelte-check clean.

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

frontend/src/lib/api/collections.test.ts

@@ -0,0 +1,158 @@
+import { describe, it, expect, vi, beforeEach, afterEach, type MockInstance } from 'vitest';
+import {
+    listMyCollections,
+    listMyCollectionsOrEmpty,
+    createCollection,
+    getCollection,
+    updateCollection,
+    deleteCollection,
+    listCollectionMangas,
+    addMangaToCollection,
+    removeMangaFromCollection,
+    getMyCollectionsContaining
+} from './collections';
+
+function ok(body: unknown, status = 200): Response {
+    return new Response(JSON.stringify(body), {
+        status,
+        headers: { 'content-type': 'application/json' }
+    });
+}
+
+function noContent(): Response {
+    return new Response(null, { status: 204 });
+}
+
+function envelope(status: number, code: string, message: string): Response {
+    return new Response(JSON.stringify({ error: { code, message } }), {
+        status,
+        headers: { 'content-type': 'application/json' }
+    });
+}
+
+function collectionFixture(extra: Record<string, unknown> = {}) {
+    return {
+        id: 'c1',
+        user_id: 'u1',
+        name: 'Favorites',
+        description: null,
+        created_at: '2026-01-01T00:00:00Z',
+        updated_at: '2026-01-01T00:00:00Z',
+        manga_count: 0,
+        sample_covers: [],
+        ...extra
+    };
+}
+
+describe('collections api client', () => {
+    let fetchSpy: MockInstance<typeof globalThis.fetch>;
+
+    beforeEach(() => {
+        fetchSpy = vi.spyOn(globalThis, 'fetch');
+    });
+    afterEach(() => {
+        vi.restoreAllMocks();
+    });
+
+    it('listMyCollections returns the paged envelope', async () => {
+        fetchSpy.mockResolvedValueOnce(
+            ok({
+                items: [collectionFixture()],
+                page: { limit: 50, offset: 0, total: 1 }
+            })
+        );
+        const result = await listMyCollections();
+        expect(result.items[0].name).toBe('Favorites');
+        const url = fetchSpy.mock.calls[0][0] as string;
+        expect(url).toMatch(/\/v1\/me\/collections$/);
+    });
+
+    it('listMyCollectionsOrEmpty returns empty page on 401', async () => {
+        fetchSpy.mockResolvedValueOnce(envelope(401, 'unauthenticated', 'login required'));
+        const result = await listMyCollectionsOrEmpty();
+        expect(result.items).toEqual([]);
+        expect(result.page.total).toBeNull();
+    });
+
+    it('listMyCollectionsOrEmpty re-throws non-401 errors', async () => {
+        fetchSpy.mockResolvedValueOnce(envelope(500, 'internal_error', 'oops'));
+        await expect(listMyCollectionsOrEmpty()).rejects.toMatchObject({ status: 500 });
+    });
+
+    it('createCollection POSTs JSON to /v1/collections', async () => {
+        fetchSpy.mockResolvedValueOnce(ok(collectionFixture(), 201));
+        const c = await createCollection({ name: 'Favorites' });
+        expect(c.name).toBe('Favorites');
+        const init = fetchSpy.mock.calls[0][1] as RequestInit;
+        expect(init.method).toBe('POST');
+        expect(JSON.parse(init.body as string)).toEqual({ name: 'Favorites' });
+    });
+
+    it('getCollection encodes the id', async () => {
+        fetchSpy.mockResolvedValueOnce(ok(collectionFixture()));
+        await getCollection('id with space');
+        const url = fetchSpy.mock.calls[0][0] as string;
+        expect(url).toContain('/v1/collections/id%20with%20space');
+    });
+
+    it('updateCollection PATCHes with the patch body', async () => {
+        fetchSpy.mockResolvedValueOnce(ok(collectionFixture({ name: 'Read later' })));
+        const updated = await updateCollection('c1', { name: 'Read later' });
+        expect(updated.name).toBe('Read later');
+        const init = fetchSpy.mock.calls[0][1] as RequestInit;
+        expect(init.method).toBe('PATCH');
+        expect(JSON.parse(init.body as string)).toEqual({ name: 'Read later' });
+    });
+
+    it('deleteCollection issues DELETE', async () => {
+        fetchSpy.mockResolvedValueOnce(noContent());
+        await deleteCollection('c1');
+        const init = fetchSpy.mock.calls[0][1] as RequestInit;
+        expect(init.method).toBe('DELETE');
+    });
+
+    it('listCollectionMangas returns the paged envelope of mangas', async () => {
+        fetchSpy.mockResolvedValueOnce(
+            ok({
+                items: [
+                    {
+                        id: 'm1',
+                        title: 'Berserk',
+                        status: 'ongoing',
+                        alt_titles: [],
+                        description: null,
+                        cover_image_path: null,
+                        created_at: '2026-01-01T00:00:00Z',
+                        updated_at: '2026-01-01T00:00:00Z'
+                    }
+                ],
+                page: { limit: 50, offset: 0, total: 1 }
+            })
+        );
+        const r = await listCollectionMangas('c1');
+        expect(r.items[0].title).toBe('Berserk');
+    });
+
+    it('addMangaToCollection POSTs the manga_id', async () => {
+        fetchSpy.mockResolvedValueOnce(ok({}, 201));
+        await addMangaToCollection('c1', 'm9');
+        const init = fetchSpy.mock.calls[0][1] as RequestInit;
+        expect(init.method).toBe('POST');
+        expect(JSON.parse(init.body as string)).toEqual({ manga_id: 'm9' });
+    });
+
+    it('removeMangaFromCollection DELETEs the nested resource', async () => {
+        fetchSpy.mockResolvedValueOnce(noContent());
+        await removeMangaFromCollection('c1', 'm9');
+        const url = fetchSpy.mock.calls[0][0] as string;
+        expect(url).toMatch(/\/v1\/collections\/c1\/mangas\/m9$/);
+    });
+
+    it('getMyCollectionsContaining returns the id list', async () => {
+        fetchSpy.mockResolvedValueOnce(ok({ collection_ids: ['c1', 'c3'] }));
+        const ids = await getMyCollectionsContaining('m1');
+        expect(ids).toEqual(['c1', 'c3']);
+        const url = fetchSpy.mock.calls[0][0] as string;
+        expect(url).toMatch(/\/v1\/mangas\/m1\/my-collections$/);
+    });
+});