完善角色与消息权限：收紧板管内容处置，彻底删除仅站长，并统一管理删帖/评弹窗。

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

backend/service/comment.go

@@ -435,6 +435,13 @@ func (s *CommentService) Delete(actor *Actor, commentID, userID uint, opts Delet
 		if actor == nil || !actor.CanModerateBoard(post.BoardID) {
 			return ErrCommentForbidden
 		}
+		var author model.User
+		if err := s.db.Select("role").First(&author, comment.UserID).Error; err != nil {
+			return ErrCommentNotFound
+		}
+		if !actor.CanModerateAuthor(author.Role) {
+			return ErrAuthorProtected
+		}
 		deleteType = strings.TrimSpace(opts.DeleteType)
 		if !model.ValidPostDeleteType(deleteType) {
 			return ErrCommentInvalidType
@@ -490,6 +497,13 @@ func (s *CommentService) Restore(actor *Actor, commentID, userID uint) error {
 			return ErrCommentNotFound
 		}
 		if actor != nil && actor.CanModerateBoard(post.BoardID) {
+			var author model.User
+			if err := s.db.Select("role").First(&author, comment.UserID).Error; err != nil {
+				return ErrCommentNotFound
+			}
+			if !actor.CanModerateAuthor(author.Role) {
+				return ErrAuthorProtected
+			}
 			allowed = true
 		}
 	}
@@ -546,6 +560,9 @@ func (s *CommentService) collectDescendantIDs(comment model.Comment) []uint {
 
 // Purge 硬删评论及子树（仅板块审核权）；不占位；对尚未软删的已发布条递减 comment_count。
 func (s *CommentService) Purge(actor *Actor, commentID, userID uint) error {
+	if actor == nil || !actor.CanPurgeContent() {
+		return ErrPurgeOwnerOnly
+	}
 	var comment model.Comment
 	if err := s.db.Unscoped().First(&comment, commentID).Error; err != nil {
 		return ErrCommentNotFound
@@ -554,7 +571,7 @@ func (s *CommentService) Purge(actor *Actor, commentID, userID uint) error {
 	if err := s.db.Select("id", "board_id").First(&post, comment.PostID).Error; err != nil {
 		return ErrCommentNotFound
 	}
-	if actor == nil || !actor.CanModerateBoard(post.BoardID) {
+	if !actor.CanModerateBoard(post.BoardID) {
 		return ErrCommentForbidden
 	}
 	_ = userID