feat(home): add a Continue-reading shelf with new-chapter badges

Surface a horizontal "Continue reading" shelf at the top of the homepage,
fed by the user's read-progress history. Each card jumps back to the exact
page they left off (deep-linking `?page=N` past the first) and flags how
many chapters have landed since — the personal new_chapters_count from the
read-progress list. The shelf is fetched after the catalogue load so the
public browse path stays unauthenticated; guests get an empty list (401
swallowed) and the shelf stays hidden.

Add new_chapters_count to the frontend ReadProgressSummary type to match
the backend. Component unit tests cover href/deep-link, badge visibility,
and the no-chapter fallback; e2e covers signed-in (shelf + badge) and
anonymous (hidden).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend/e2e/continue-reading-shelf.spec.ts

@@ -0,0 +1,89 @@
+import { test, expect, type Page } from './fixtures';
+
+// The homepage "Continue reading" shelf: visible with a per-manga new-chapter
+// badge when the user has reading history, and absent for anonymous visitors
+// (the read-progress fetch 401s → empty → hidden).
+
+const emptyMangas = { items: [], page: { limit: 50, offset: 0, total: 0 } };
+
+async function mockCommon(page: Page) {
+    await page.route('**/api/v1/auth/config', (route) =>
+        route.fulfill({
+            status: 200,
+            contentType: 'application/json',
+            body: JSON.stringify({ self_register_enabled: true, private_mode: false })
+        })
+    );
+    await page.route('**/api/v1/genres*', (route) =>
+        route.fulfill({ status: 200, contentType: 'application/json', body: '[]' })
+    );
+    await page.route('**/api/v1/mangas*', (route) =>
+        route.fulfill({
+            status: 200,
+            contentType: 'application/json',
+            body: JSON.stringify(emptyMangas)
+        })
+    );
+}
+
+test('shows the continue-reading shelf with a new-chapter badge when signed in', async ({ page }) => {
+    await mockCommon(page);
+    await page.route('**/api/v1/auth/me', (route) =>
+        route.fulfill({
+            status: 200,
+            contentType: 'application/json',
+            body: JSON.stringify({ user: { id: 'u1', username: 'reader', is_admin: false } })
+        })
+    );
+    await page.route('**/api/v1/me/read-progress*', (route) =>
+        route.fulfill({
+            status: 200,
+            contentType: 'application/json',
+            body: JSON.stringify({
+                items: [
+                    {
+                        manga_id: 'm1',
+                        manga_title: 'Berserk',
+                        manga_cover_image_path: null,
+                        chapter_id: 'c1',
+                        chapter_number: 3,
+                        page: 4,
+                        updated_at: '2026-01-01T00:00:00Z',
+                        new_chapters_count: 2
+                    }
+                ],
+                page: { limit: 50, offset: 0, total: 1 }
+            })
+        })
+    );
+
+    await page.goto('/');
+
+    const card = page.getByTestId('continue-card-m1');
+    await expect(card).toBeVisible();
+    await expect(card).toHaveAttribute('href', '/manga/m1/chapter/c1?page=4');
+    await expect(page.getByTestId('continue-new-badge-m1')).toContainText('2');
+});
+
+test('hides the continue-reading shelf for anonymous visitors', async ({ page }) => {
+    await mockCommon(page);
+    await page.route('**/api/v1/auth/me', (route) =>
+        route.fulfill({
+            status: 401,
+            contentType: 'application/json',
+            body: JSON.stringify({ error: { code: 'unauthenticated', message: 'no' } })
+        })
+    );
+    await page.route('**/api/v1/me/read-progress*', (route) =>
+        route.fulfill({
+            status: 401,
+            contentType: 'application/json',
+            body: JSON.stringify({ error: { code: 'unauthenticated', message: 'no' } })
+        })
+    );
+
+    await page.goto('/');
+    // The catalogue heading confirms the page rendered before asserting absence.
+    await expect(page.getByRole('heading', { name: 'Mangas' })).toBeVisible();
+    await expect(page.getByTestId('continue-shelf')).toHaveCount(0);
+});