feat(audit): add COMMENT_ADDED and MENTION_CREATED audit events

Instruments CommentService.postComment(), postBlockComment(), and
replyToComment() to fire COMMENT_ADDED after each successful save and
MENTION_CREATED once per mentioned user. The shared logCommentPosted()
helper avoids duplicating the two-call pattern across all three post
methods.

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

backend/src/main/java/org/raddatz/familienarchiv/audit/AuditKind.java

@@ -19,4 +19,10 @@ public enum AuditKind {
 
     /** Payload: {@code {"pageNumber": 3}} */
     ANNOTATION_CREATED,
+
+    /** Payload: {@code {"commentId": "uuid"}} */
+    COMMENT_ADDED,
+
+    /** Payload: {@code {"commentId": "uuid", "mentionedUserId": "uuid"}} */
+    MENTION_CREATED,
 }

backend/src/main/java/org/raddatz/familienarchiv/service/CommentService.java

@@ -1,6 +1,8 @@
 package org.raddatz.familienarchiv.service;
 
 import lombok.RequiredArgsConstructor;
+import org.raddatz.familienarchiv.audit.AuditKind;
+import org.raddatz.familienarchiv.audit.AuditService;
 import org.raddatz.familienarchiv.dto.MentionDTO;
 import org.raddatz.familienarchiv.exception.DomainException;
 import org.raddatz.familienarchiv.exception.ErrorCode;
@@ -12,6 +14,7 @@ import org.springframework.transaction.annotation.Transactional;
 
 import java.util.LinkedHashSet;
 import java.util.List;
+import java.util.Map;
 import java.util.Set;
 import java.util.UUID;
 
@@ -22,6 +25,7 @@ public class CommentService {
     private final CommentRepository commentRepository;
     private final UserService userService;
     private final NotificationService notificationService;
+    private final AuditService auditService;
 
     public List<DocumentComment> getCommentsForDocument(UUID documentId) {
         List<DocumentComment> roots =
@@ -53,6 +57,7 @@ public class CommentService {
         DocumentComment saved = commentRepository.save(comment);
         withMentionDTOs(saved);
         notificationService.notifyMentions(mentionedUserIds, saved);
+        logCommentPosted(author, documentId, saved, mentionedUserIds);
         return saved;
     }
 
@@ -70,6 +75,7 @@ public class CommentService {
         DocumentComment saved = commentRepository.save(comment);
         withMentionDTOs(saved);
         notificationService.notifyMentions(mentionedUserIds, saved);
+        logCommentPosted(author, documentId, saved, mentionedUserIds);
         return saved;
     }
 
@@ -101,6 +107,7 @@ public class CommentService {
         participantIds.remove(author.getId());
         notificationService.notifyReply(saved, participantIds);
         notificationService.notifyMentions(mentionedUserIds, saved);
+        logCommentPosted(author, documentId, saved, mentionedUserIds);
         return saved;
     }
 
@@ -171,6 +178,17 @@ public class CommentService {
                         ErrorCode.COMMENT_NOT_FOUND, "Comment not found: " + commentId));
     }
 
+    private void logCommentPosted(AppUser author, UUID documentId, DocumentComment saved, List<UUID> mentionedUserIds) {
+        UUID actorId = author != null ? author.getId() : null;
+        String commentId = saved.getId().toString();
+        auditService.logAfterCommit(AuditKind.COMMENT_ADDED, actorId, documentId, Map.of("commentId", commentId));
+        if (mentionedUserIds != null) {
+            mentionedUserIds.forEach(mentionedUserId ->
+                    auditService.logAfterCommit(AuditKind.MENTION_CREATED, actorId, documentId,
+                            Map.of("commentId", commentId, "mentionedUserId", mentionedUserId.toString())));
+        }
+    }
+
     private String resolveAuthorName(AppUser author) {
         String first = author.getFirstName();
         String last = author.getLastName();