fix(e2e): fix annotation delete test and harden comments fetch

- Add aria-label="Kommentare anzeigen" to annotation container div so
  getByRole('button', { name: /annotation löschen/i }) no longer
  matches the container (its name was previously inherited from the
  child delete button, causing the test to click the wrong element)
- Wrap the server-side comments fetch in a .catch and try/catch so a
  network error or non-JSON response never crashes the document load

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

frontend/src/lib/components/AnnotationLayer.svelte

@@ -120,6 +120,7 @@ const containerStyle = $derived(
 			data-annotation
 			role="button"
 			tabindex="0"
+			aria-label="Kommentare anzeigen"
 			onclick={() => onAnnotationClick?.(annotation.id)}
 			onkeydown={(e) => { if (e.key === 'Enter' || e.key === ' ') onAnnotationClick?.(annotation.id); }}
 			onmouseenter={() => (hoveredId = annotation.id)}

frontend/src/routes/documents/[id]/+page.server.ts

@@ -10,7 +10,7 @@ export async function load({ params, fetch }) {
 
 	const [docResult, commentsRes] = await Promise.all([
 		api.GET('/api/documents/{id}', { params: { path: { id } } }),
-		fetch(`${base}/api/documents/${id}/comments`)
+		fetch(`${base}/api/documents/${id}/comments`).catch(() => null)
 	]);
 
 	if (docResult.response.status === 401) throw redirect(302, '/login');
@@ -20,7 +20,14 @@ export async function load({ params, fetch }) {
 		throw error(docResult.response.status, getErrorMessage(code));
 	}
 
-	const comments = commentsRes.ok ? await commentsRes.json() : [];
+	let comments: unknown[] = [];
+	if (commentsRes?.ok) {
+		try {
+			comments = await commentsRes.json();
+		} catch {
+			// ignore invalid response
+		}
+	}
 
 	return { document: docResult.data!, comments };
 }