feat(korrespondenz): address PR #164 review – blockers and suggestions

Blockers (14):
- B1: fix senderName/receiverName to use $derived instead of $state + sync $effect
- B2: migrate all korrespondenz components from messages-extra shim to paraglide m.*
- B3: i18n CorrespondenzEmptyState (heading, subtext, search placeholder)
- B4: add response.ok checks to admin layout server load
- B5: add response.ok checks to korrespondenz page server load
- B6: add page.server.spec.ts with 5 test suites for korrespondenz load function
- B7: add axe-core accessibility checks to all e2e korrespondenz tests
- B8: add Testcontainers JPQL tests for findSinglePersonCorrespondence (DISTINCT + sender)
- B9: hide auth reset-token endpoint from OpenAPI spec; remove from generated api.ts
- B11: replace amber hardcoded hex colors in SinglePersonHintBar with brand tokens
- B12: replace clipboard emoji with Heroicons SVG in SinglePersonHintBar
- B13: create DateInput component (German dd.mm.yyyy); use it in CorrespondenzFilterControls
- B14: add Paraglide compile step to CI workflow before lint/test

Suggestions (11):
- S1: make CorrespondentSuggestionsDropdown a pure display component; lift fetch to PersonBar
- S2: fix leftover messages-extra import in ConversationTimeline; use brand tokens for status dots
- S3: add intent comment to EntityNav openFlyout behavior
- S4: rename canManageGroups → canManagePermissions throughout admin
- S6: remove domFlush helper from DateInput spec; use expect.poll instead
- S7: replace test.skip with throw new Error in bilateral e2e tests
- S8: add inverse aria-disabled test for filter strip
- S9: remove sm:min-h-0 from sort button to preserve 44px touch target
- S10: add title attributes to tablet trigger buttons in EntityNav
- S11: delete messages-extra.ts shim entirely

Also: fix admin pages revealing blank strip at bottom (-mb-6 on admin layout)

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

frontend/e2e/korrespondenz.spec.ts

@@ -1,9 +1,16 @@
 import { test, expect } from '@playwright/test';
+import AxeBuilder from '@axe-core/playwright';
+
+function buildAxe(page: Parameters<typeof AxeBuilder>[0]['page']) {
+	return new AxeBuilder({ page }).withTags(['wcag2a', 'wcag2aa']);
+}
 
 test.describe('Korrespondenz – empty state', () => {
 	test('shows the search heading when no person is selected', async ({ page }) => {
 		await page.goto('/korrespondenz');
 		await expect(page.getByText(/Korrespondenz durchsuchen/i)).toBeVisible();
+		const a11y = await buildAxe(page).analyze();
+		expect(a11y.violations, JSON.stringify(a11y.violations, null, 2)).toHaveLength(0);
 		await page.screenshot({ path: 'test-results/e2e/korrespondenz-empty.png' });
 	});
 
@@ -37,6 +44,8 @@ test.describe('Korrespondenz – single-person mode', () => {
 		const filterStrip = page.locator('[aria-disabled="false"]').first();
 		await expect(filterStrip).toBeAttached();
 
+		const a11y = await buildAxe(page).analyze();
+		expect(a11y.violations, JSON.stringify(a11y.violations, null, 2)).toHaveLength(0);
 		await page.screenshot({ path: 'test-results/e2e/korrespondenz-single-person.png' });
 	});
 
@@ -75,10 +84,14 @@ test.describe('Korrespondenz – bilateral mode', () => {
 			// Hint bar should NOT be shown in bilateral mode
 			await expect(page.getByText(/Alle Briefe von/i)).not.toBeVisible();
 
+			const a11y = await buildAxe(page).analyze();
+			expect(a11y.violations, JSON.stringify(a11y.violations, null, 2)).toHaveLength(0);
 			await page.screenshot({ path: 'test-results/e2e/korrespondenz-bilateral.png' });
 		} else {
-			// No bilateral data available for this person — skip with a note
-			test.skip(true, `No bilateral correspondent links found for person ${senderId}`);
+			// E2E seed must include bilateral correspondents — a missing link is a test failure.
+			throw new Error(
+				`No bilateral correspondent links found for person ${senderId}. Ensure the E2E seed contains at least one bilateral correspondence pair.`
+			);
 		}
 	});