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/service/admin_user_service.go

@@ -0,0 +1,145 @@
+package service
+
+import (
+	"context"
+
+	"carrot_bbs/internal/dto"
+	"carrot_bbs/internal/model"
+	"carrot_bbs/internal/repository"
+)
+
+// AdminUserService 管理端用户服务接口
+type AdminUserService interface {
+	// GetUserList 获取用户列表（分页、搜索、状态筛选）
+	GetUserList(ctx context.Context, page, pageSize int, keyword, status string) ([]dto.AdminUserListResponse, int64, error)
+	// GetUserDetail 获取用户详情（含统计信息）
+	GetUserDetail(ctx context.Context, userID string) (*dto.AdminUserDetailResponse, error)
+	// UpdateUserStatus 更新用户状态
+	UpdateUserStatus(ctx context.Context, userID string, status model.UserStatus) (*dto.AdminUserDetailResponse, error)
+}
+
+// adminUserServiceImpl 管理端用户服务实现
+type adminUserServiceImpl struct {
+	userRepo *repository.UserRepository
+}
+
+// NewAdminUserService 创建管理端用户服务
+func NewAdminUserService(userRepo *repository.UserRepository) AdminUserService {
+	return &adminUserServiceImpl{
+		userRepo: userRepo,
+	}
+}
+
+// GetUserList 获取用户列表
+func (s *adminUserServiceImpl) GetUserList(ctx context.Context, page, pageSize int, keyword, status string) ([]dto.AdminUserListResponse, int64, error) {
+	users, total, err := s.userRepo.AdminList(page, pageSize, keyword, status)
+	if err != nil {
+		return nil, 0, err
+	}
+
+	responses := make([]dto.AdminUserListResponse, len(users))
+	for i, user := range users {
+		responses[i] = convertUserToAdminListResponse(user)
+	}
+
+	return responses, total, nil
+}
+
+// GetUserDetail 获取用户详情
+func (s *adminUserServiceImpl) GetUserDetail(ctx context.Context, userID string) (*dto.AdminUserDetailResponse, error) {
+	user, err := s.userRepo.GetByID(userID)
+	if err != nil {
+		return nil, err
+	}
+
+	// 获取帖子数
+	postsCount, _ := s.userRepo.GetPostsCount(userID)
+
+	// 获取评论数
+	commentsCount, _ := s.userRepo.GetCommentsCount(userID)
+
+	return convertUserToAdminDetailResponse(user, postsCount, commentsCount), nil
+}
+
+// UpdateUserStatus 更新用户状态
+func (s *adminUserServiceImpl) UpdateUserStatus(ctx context.Context, userID string, status model.UserStatus) (*dto.AdminUserDetailResponse, error) {
+	// 先检查用户是否存在
+	user, err := s.userRepo.GetByID(userID)
+	if err != nil {
+		return nil, err
+	}
+
+	// 更新状态
+	if err := s.userRepo.UpdateStatus(userID, status); err != nil {
+		return nil, err
+	}
+
+	// 重新获取用户信息
+	user, err = s.userRepo.GetByID(userID)
+	if err != nil {
+		return nil, err
+	}
+
+	// 获取统计信息
+	postsCount, _ := s.userRepo.GetPostsCount(userID)
+	commentsCount, _ := s.userRepo.GetCommentsCount(userID)
+
+	return convertUserToAdminDetailResponse(user, postsCount, commentsCount), nil
+}
+
+// convertUserToAdminListResponse 转换用户为管理端列表响应
+func convertUserToAdminListResponse(user *model.User) dto.AdminUserListResponse {
+	var lastLoginAt string
+	if user.LastLoginAt != nil {
+		lastLoginAt = user.LastLoginAt.Format("2006-01-02 15:04:05")
+	}
+
+	return dto.AdminUserListResponse{
+		ID:             user.ID,
+		Username:       user.Username,
+		Nickname:       user.Nickname,
+		Email:          user.Email,
+		Phone:          user.Phone,
+		EmailVerified:  user.EmailVerified,
+		Avatar:         user.Avatar,
+		Status:         string(user.Status),
+		PostsCount:     user.PostsCount,
+		FollowersCount: user.FollowersCount,
+		FollowingCount: user.FollowingCount,
+		LastLoginAt:    lastLoginAt,
+		LastLoginIP:    user.LastLoginIP,
+		CreatedAt:      user.CreatedAt.Format("2006-01-02 15:04:05"),
+	}
+}
+
+// convertUserToAdminDetailResponse 转换用户为管理端详情响应
+func convertUserToAdminDetailResponse(user *model.User, postsCount, commentsCount int64) *dto.AdminUserDetailResponse {
+	var lastLoginAt string
+	if user.LastLoginAt != nil {
+		lastLoginAt = user.LastLoginAt.Format("2006-01-02 15:04:05")
+	}
+
+	return &dto.AdminUserDetailResponse{
+		ID:             user.ID,
+		Username:       user.Username,
+		Nickname:       user.Nickname,
+		Email:          user.Email,
+		Phone:          user.Phone,
+		EmailVerified:  user.EmailVerified,
+		Avatar:         user.Avatar,
+		CoverURL:       user.CoverURL,
+		Bio:            user.Bio,
+		Website:        user.Website,
+		Location:       user.Location,
+		IsVerified:     user.IsVerified,
+		Status:         string(user.Status),
+		PostsCount:     int(postsCount),
+		CommentsCount:  commentsCount,
+		FollowersCount: user.FollowersCount,
+		FollowingCount: user.FollowingCount,
+		LastLoginAt:    lastLoginAt,
+		LastLoginIP:    user.LastLoginIP,
+		CreatedAt:      user.CreatedAt.Format("2006-01-02 15:04:05"),
+		UpdatedAt:      user.UpdatedAt.Format("2006-01-02 15:04:05"),
+	}
+}