修复：管理员默认商户与账户设置

backend/internal/service/auth.go

@@ -26,6 +26,13 @@ type LoginResult struct {
 	User  *model.User `json:"user"`
 }
 
+type UpdateCurrentAccountInput struct {
+	CurrentPassword string
+	Username        string
+	Nickname        string
+	NewPassword     string
+}
+
 func (s *AuthService) Login(username, password string) (*LoginResult, error) {
 	var user model.User
 	if err := s.db.Where("username = ?", username).First(&user).Error; err != nil {
@@ -86,6 +93,67 @@ func (s *AuthService) ChangePassword(userID uint, currentPassword, newPassword s
 	return s.db.Model(&user).Update("password_hash", string(hash)).Error
 }
 
+// UpdateCurrentAccount lets a user maintain their own login identity. The
+// current password is always required before username, nickname, or password
+// changes are accepted.
+func (s *AuthService) UpdateCurrentAccount(userID uint, in UpdateCurrentAccountInput) (*model.User, error) {
+	if userID == 0 {
+		return nil, errors.New("无效的用户身份")
+	}
+	in.Username = strings.TrimSpace(in.Username)
+	if len(in.Username) < 3 || len(in.Username) > 64 {
+		return nil, errors.New("用户名长度需为 3 至 64 位")
+	}
+	if len(in.Nickname) > 64 {
+		return nil, errors.New("昵称不能超过 64 位")
+	}
+	if in.NewPassword != "" && len(in.NewPassword) < 8 {
+		return nil, errors.New("新密码至少 8 位")
+	}
+
+	updated := &model.User{}
+	err := s.db.Transaction(func(tx *gorm.DB) error {
+		var user model.User
+		if err := tx.First(&user, userID).Error; err != nil {
+			if errors.Is(err, gorm.ErrRecordNotFound) {
+				return errors.New("用户不存在")
+			}
+			return err
+		}
+		if err := bcrypt.CompareHashAndPassword([]byte(user.PasswordHash), []byte(in.CurrentPassword)); err != nil {
+			return errors.New("当前密码错误")
+		}
+		if in.Username != user.Username {
+			var count int64
+			if err := tx.Model(&model.User{}).Where("username = ? AND id <> ?", in.Username, user.ID).Count(&count).Error; err != nil {
+				return err
+			}
+			if count > 0 {
+				return errors.New("用户名已存在")
+			}
+		}
+		updates := map[string]interface{}{"username": in.Username, "nickname": in.Nickname}
+		if in.NewPassword != "" {
+			if err := bcrypt.CompareHashAndPassword([]byte(user.PasswordHash), []byte(in.NewPassword)); err == nil {
+				return errors.New("新密码不能与当前密码相同")
+			}
+			hash, err := bcrypt.GenerateFromPassword([]byte(in.NewPassword), bcrypt.DefaultCost)
+			if err != nil {
+				return err
+			}
+			updates["password_hash"] = string(hash)
+		}
+		if err := tx.Model(&user).Updates(updates).Error; err != nil {
+			return err
+		}
+		return tx.First(updated, user.ID).Error
+	})
+	if err != nil {
+		return nil, err
+	}
+	return updated, nil
+}
+
 // EnsureAdmin creates the first platform administrator for an empty database.
 // Existing administrator accounts are never changed by environment variables.
 func (s *AuthService) EnsureAdmin(username, password string) error {