feat(comments): 支持编辑与管理可见历史，采纳展示改用楼层号

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/service/admin_content.go

@@ -442,5 +442,10 @@ func (s *ModerationService) PurgeComment(actor *Actor, id uint) error {
 	if !cm.DeletedAt.Valid {
 		return ErrContentNotDeleted
 	}
-	return s.db.Unscoped().Delete(&model.Comment{}, id).Error
+	return s.db.Transaction(func(tx *gorm.DB) error {
+		if err := tx.Where("comment_id = ?", id).Delete(&model.CommentEditHistory{}).Error; err != nil {
+			return err
+		}
+		return tx.Unscoped().Delete(&model.Comment{}, id).Error
+	})
 }