fix(review): address reviewer concerns from PR #661

- Replace brittle createdAt===updatedAt isNew() check with a 7-day
  recency window (created within last 7 days = new)
- Add createdAt/updatedAt to searchItem fixture in page.server.spec.ts
  and assert they are propagated to recentDocs
- Replace null timestamps in DocumentListItem test fixtures with a fixed
  LocalDateTime to satisfy the @Schema(required) contract

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/lib/shared/dashboard/ReaderRecentDocs.svelte.test.ts

@@ -31,25 +31,25 @@ describe('ReaderRecentDocs', () => {
 			.toHaveAttribute('href', '/documents');
 	});
 
-	it('renders the New badge when createdAt equals updatedAt', async () => {
+	it('renders the New badge when document was created within the last 7 days', async () => {
+		const recentDate = new Date(Date.now() - 2 * 24 * 60 * 60 * 1000).toISOString();
+		const laterUpdate = new Date(Date.now() - 1 * 24 * 60 * 60 * 1000).toISOString();
 		render(ReaderRecentDocs, {
 			props: {
-				documents: [
-					makeDoc({ createdAt: '2026-04-15T10:00:00Z', updatedAt: '2026-04-15T10:00:00Z' })
-				]
+				documents: [makeDoc({ createdAt: recentDate, updatedAt: laterUpdate })]
 			}
 		});
 
 		await expect.element(page.getByText('Neu')).toBeVisible();
 	});
 
-	it('hides the New badge when document was updated after creation', async () => {
+	it('hides the New badge when document was created more than 7 days ago', async () => {
 		render(ReaderRecentDocs, {
 			props: {
 				documents: [
 					makeDoc({
 						createdAt: '2026-04-15T10:00:00Z',
-						updatedAt: '2026-04-15T11:00:00Z'
+						updatedAt: '2026-04-15T10:00:00Z'
 					})
 				]
 			}