refactor(comment): remove dead findAnnotationIdsByIds; fix aria-label i18n; rename misleading test

- Remove `findAnnotationIdsByIds` from CommentService — no production caller exists now
  that DashboardService uses `findDataByIds` directly; along with its test coverage
- Fix aria-label construction in ChronikRow: pass actorName to i18n message function
  instead of manually prepending the actor, so all locales render correctly
- Rename `findDataByIds_does_not_truncate_at_exactly_120_chars` →
  `findDataByIds_preserves_content_at_exactly_120_chars` for accurate description

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

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

@@ -24,7 +24,6 @@ import java.util.List;
 import java.util.Map;
 import java.util.Set;
 import java.util.UUID;
-import java.util.stream.Collectors;
 
 @Service
 @RequiredArgsConstructor
@@ -49,12 +48,6 @@ public class CommentService {
         return result;
     }
 
-    public Map<UUID, UUID> findAnnotationIdsByIds(Collection<UUID> commentIds) {
-        return findDataByIds(commentIds).entrySet().stream()
-                .filter(e -> e.getValue().annotationId() != null)
-                .collect(Collectors.toMap(Map.Entry::getKey, e -> e.getValue().annotationId()));
-    }
-
     private String stripAndTruncate(String html) {
         if (html == null || html.isBlank()) return "";
         String text = Jsoup.parse(html).text().trim();