feat(admin): add comprehensive admin management system

- Add admin handlers and services for users, posts, comments, groups, and dashboard
- Implement role permission management with ability to view and update permissions
- Add database seeding for roles and Casbin permission policies
- Upgrade Casbin from v2 to v3 with GORM adapter for persistent policy storage
- Add admin-specific repository methods with filtering and pagination
- Register new admin API routes under /api/v1/admin/*

internal/repository/comment_repo.go

@@ -298,3 +298,96 @@ func (r *CommentRepository) IsLiked(commentID, userID string) bool {
 	r.db.Model(&model.CommentLike{}).Where("comment_id = ? AND user_id = ?", commentID, userID).Count(&count)
 	return count > 0
 }
+
+// AdminCommentListFilter 管理端评论列表筛选条件
+type AdminCommentListFilter struct {
+	Keyword   string
+	PostID    string
+	AuthorID  string
+	Status    string
+	StartDate string
+	EndDate   string
+	Page      int
+	PageSize  int
+}
+
+// GetAdminCommentList 获取管理端评论列表
+func (r *CommentRepository) GetAdminCommentList(filter AdminCommentListFilter) ([]*model.Comment, int64, error) {
+	var comments []*model.Comment
+	var total int64
+
+	query := r.db.Model(&model.Comment{}).Preload("User")
+
+	// 应用筛选条件
+	if filter.Keyword != "" {
+		query = query.Where("content LIKE ?", "%"+filter.Keyword+"%")
+	}
+	if filter.PostID != "" {
+		query = query.Where("post_id = ?", filter.PostID)
+	}
+	if filter.AuthorID != "" {
+		query = query.Where("user_id = ?", filter.AuthorID)
+	}
+	if filter.Status != "" {
+		query = query.Where("status = ?", filter.Status)
+	}
+	if filter.StartDate != "" {
+		query = query.Where("created_at >= ?", filter.StartDate)
+	}
+	if filter.EndDate != "" {
+		query = query.Where("created_at <= ?", filter.EndDate+" 23:59:59")
+	}
+
+	// 统计总数
+	if err := query.Count(&total).Error; err != nil {
+		return nil, 0, err
+	}
+
+	// 分页查询
+	offset := (filter.Page - 1) * filter.PageSize
+	if err := query.Offset(offset).Limit(filter.PageSize).Order("created_at DESC").Find(&comments).Error; err != nil {
+		return nil, 0, err
+	}
+
+	return comments, total, nil
+}
+
+// GetAdminCommentByID 获取管理端评论详情（包含关联信息）
+func (r *CommentRepository) GetAdminCommentByID(id string) (*model.Comment, error) {
+	var comment model.Comment
+	err := r.db.Preload("User").First(&comment, "id = ?", id).Error
+	if err != nil {
+		return nil, err
+	}
+	return &comment, nil
+}
+
+// BatchDelete 批量删除评论
+func (r *CommentRepository) BatchDelete(ids []string) ([]string, error) {
+	var failedIDs []string
+
+	for _, id := range ids {
+		if err := r.Delete(id); err != nil {
+			failedIDs = append(failedIDs, id)
+		}
+	}
+
+	return failedIDs, nil
+}
+
+// GetCommentsByPostIDForAdmin 管理端获取帖子的评论列表（包含所有状态）
+func (r *CommentRepository) GetCommentsByPostIDForAdmin(postID string, page, pageSize int) ([]*model.Comment, int64, error) {
+	var comments []*model.Comment
+	var total int64
+
+	r.db.Model(&model.Comment{}).Where("post_id = ?", postID).Count(&total)
+
+	offset := (page - 1) * pageSize
+	err := r.db.Where("post_id = ?", postID).
+		Preload("User").
+		Offset(offset).Limit(pageSize).
+		Order("created_at DESC").
+		Find(&comments).Error
+
+	return comments, total, err
+}