feat: @提及支持改名后链接跟随UID + 显示名自动更新

- comment_mentions新增original_username列，创建时记录原始@用户名
- Mentions map改为{original_username: {uid, name}}结构，name为当前显示名
- 用户改名后：旧@文本仍能匹配original_username，链接跟随uid不变，显示名自动更新
- 前端renderMentions适配新结构

internal/model/comment.go

@@ -25,16 +25,23 @@ type Comment struct {
 	ReplyToName string `gorm:"-:migration;<-:false" json:"reply_to_name,omitempty"`
 	// RepliesCount 回复数（非DB字段，查询填充）
 	RepliesCount int `gorm:"-:migration;<-:false" json:"replies_count,omitempty"`
-	// Mentions 有效@提及映射 username -> uid（非DB字段，批量查询填充）
-	// 前端据此判断 @username 是否为有效提及并生成链接
-	Mentions map[string]uint `gorm:"-" json:"mentions,omitempty"`
+	// Mentions 有效@提及映射 original_username -> {uid, 当前显示名}（非DB字段，批量查询填充）
+	// key=创建时的原始@用户名，value={uid,当前显示名}，用户改名后链接仍有效且显示新名
+	Mentions map[string]MentionInfo `gorm:"-" json:"mentions,omitempty"`
 }
 
-// CommentMention @提及映射（绑定UID，不是username，支持改名后自动更新显示名）
+// CommentMention @提及映射（绑定UID + 原始用户名，支持改名后自动更新显示名）
 type CommentMention struct {
-	ID        uint   `gorm:"primarykey" json:"id"`
-	CommentID uint   `gorm:"uniqueIndex:idx_comment_uid,priority:1;not null" json:"comment_id"`
-	UID       uint   `gorm:"uniqueIndex:idx_comment_uid,priority:2;not null" json:"uid"`
+	ID               uint   `gorm:"primarykey" json:"id"`
+	CommentID        uint   `gorm:"uniqueIndex:idx_comment_uid,priority:1;not null" json:"comment_id"`
+	UID              uint   `gorm:"uniqueIndex:idx_comment_uid,priority:2;not null" json:"uid"`
+	OriginalUsername string `gorm:"type:varchar(64);not null;default:''" json:"original_username"`
+}
+
+// MentionInfo @提及显示信息（前端渲染用）
+type MentionInfo struct {
+	UID  uint   `json:"uid"`
+	Name string `json:"name"` // 当前显示名
 }
 
 // UserSearchResult @搜索用户结果

internal/repository/comment_mention_repo.go

@@ -17,8 +17,9 @@ func (r *CommentRepo) FindMentionsByComment(commentID uint) ([]model.CommentMent
 	return list, err
 }
 
-// LoadMentionsForComments 批量加载多条评论的有效@提及映射（username -> uid）
-// 传入的 comments 会被原地修改，填充 Mentions 字段
+// LoadMentionsForComments 批量加载多条评论的有效@提及映射
+// key=创建时的原始@用户名, value={uid, 用户当前显示名}
+// 用户改名后：原始名匹配body中的旧@文本，显示名随users表更新
 func (r *CommentRepo) LoadMentionsForComments(comments []model.Comment) error {
 	if len(comments) == 0 {
 		return nil
@@ -29,15 +30,15 @@ func (r *CommentRepo) LoadMentionsForComments(comments []model.Comment) error {
 		commentIDs[i] = c.ID
 	}
 
-	// 查询 comment_mentions JOIN users，拿到 username 和 uid
 	type mentionRow struct {
-		CommentID uint
-		UID       uint
-		Username  string
+		CommentID        uint
+		UID              uint
+		OriginalUsername string
+		CurrentName      string
 	}
 	var rows []mentionRow
 	err := r.db.Table("comment_mentions").
-		Select("comment_mentions.comment_id, comment_mentions.uid, users.username").
+		Select("comment_mentions.comment_id, comment_mentions.uid, comment_mentions.original_username, users.username AS current_name").
 		Joins("LEFT JOIN users ON users.id = comment_mentions.uid").
 		Where("comment_mentions.comment_id IN ?", commentIDs).
 		Find(&rows).Error
@@ -45,13 +46,16 @@ func (r *CommentRepo) LoadMentionsForComments(comments []model.Comment) error {
 		return err
 	}
 
-	// 按 comment_id 分组
-	mentionMap := make(map[uint]map[string]uint)
+	// 按 comment_id 分组，key = original_username, value = MentionInfo
+	mentionMap := make(map[uint]map[string]model.MentionInfo)
 	for _, row := range rows {
 		if mentionMap[row.CommentID] == nil {
-			mentionMap[row.CommentID] = make(map[string]uint)
+			mentionMap[row.CommentID] = make(map[string]model.MentionInfo)
+		}
+		mentionMap[row.CommentID][row.OriginalUsername] = model.MentionInfo{
+			UID:  row.UID,
+			Name: row.CurrentName,
 		}
-		mentionMap[row.CommentID][row.Username] = row.UID
 	}
 
 	for i := range comments {

internal/service/comment_service.go

@@ -222,8 +222,9 @@ func (s *CommentService) parseMentions(commentID uint, body string) {
 		rows, _ := s.repo.SearchUsersByLevel(username, 2, 1)
 		if len(rows) > 0 {
 			_ = s.repo.CreateMention(&model.CommentMention{
-				CommentID: commentID,
-				UID:       rows[0].UID,
+				CommentID:        commentID,
+				UID:              rows[0].UID,
+				OriginalUsername: username,
 			})
 		}
 	}