fix(review): address review blockers from PR #475

- CommentData.java: add @Nullable on annotationId to match codebase convention
- DashboardService: isEmpty() → isBlank() for commentPreview null-guard
- ChronikRow.svelte: always set aria-label on comment rows (not only when preview present)
- ChronikRow.svelte.spec.ts: add test for aria-label on comment row without preview

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

backend/src/main/java/org/raddatz/familienarchiv/dashboard/DashboardService.java

@@ -149,7 +149,7 @@ public class DashboardService {
             UUID commentId = row.getCommentId();
             CommentData commentData = commentId != null ? commentDataByComment.get(commentId) : null;
             UUID annotationId = commentData != null ? commentData.annotationId() : null;
-            String commentPreview = commentData != null && !commentData.preview().isEmpty()
+            String commentPreview = commentData != null && !commentData.preview().isBlank()
                     ? commentData.preview() : null;
             return new ActivityFeedItemDTO(
                     org.raddatz.familienarchiv.audit.AuditKind.valueOf(row.getKind()),

backend/src/main/java/org/raddatz/familienarchiv/document/comment/CommentData.java

@@ -1,5 +1,6 @@
 package org.raddatz.familienarchiv.document.comment;
 
+import jakarta.annotation.Nullable;
 import java.util.UUID;
 
-public record CommentData(UUID annotationId, String preview) {}
+public record CommentData(@Nullable UUID annotationId, String preview) {}

frontend/src/lib/activity/ChronikRow.svelte

@@ -108,8 +108,10 @@ const rowHref: string = $derived(
 <a
 	href={rowHref}
 	data-variant={variant}
-	aria-label={variant === 'comment' && item.commentPreview
-		? `${m.chronik_comment_added({ actor: actorName, doc: docTitle })} — ${item.commentPreview}`
+	aria-label={variant === 'comment'
+		? item.commentPreview
+			? `${m.chronik_comment_added({ actor: actorName, doc: docTitle })} — ${item.commentPreview}`
+			: m.chronik_comment_added({ actor: actorName, doc: docTitle })
 		: undefined}
 	class="group flex items-start gap-3 p-3 transition-colors hover:bg-muted/50 focus-visible:ring-2 focus-visible:ring-focus-ring focus-visible:outline-none
 		{variant === 'for-you' ? 'border-l-[3px] border-accent bg-accent-bg/10' : ''}"

frontend/src/lib/activity/ChronikRow.svelte.spec.ts

@@ -229,6 +229,18 @@ describe('ChronikRow', () => {
 		expect(link?.getAttribute('aria-label')).toContain('A wonderful letter from grandma');
 	});
 
+	it('link still has aria-label for comment variant when commentPreview is absent', async () => {
+		const item: ActivityFeedItemDTO = {
+			...baseItem,
+			kind: 'COMMENT_ADDED',
+			commentPreview: undefined
+		};
+		render(ChronikRow, { item });
+		const link = document.querySelector('a[aria-label]');
+		expect(link).not.toBeNull();
+		expect(link?.getAttribute('aria-label')).not.toBeNull();
+	});
+
 	// --- robustness: title rendering for edge cases ---
 	it('still renders the row link when documentTitle is an empty string', async () => {
 		// Felix: verbText.indexOf(docTitle) returned 0 for empty titles — the span