feat(admin): 添加模型算力点配置和扣费功能

- 在管理后台设置页面添加模型算力点配置表格
- 实现后端AI接口调用时按模型扣除用户算力点
- 添加算力点余额检查和不足时的错误处理
- 在credit_logs中记录AI调用消费流水
- 更新前端远程调用后刷新用户信息显示
- 文档中补充模型算力点配置说明

repository/user.go

@@ -79,6 +79,31 @@ func SaveUser(user model.User) (model.User, error) {
 	return user, db.Save(&user).Error
 }
 
+func HasUserCredits(id string, credits int) (bool, error) {
+	user, ok, err := GetUserByID(id)
+	return ok && user.Credits >= credits, err
+}
+
+func ConsumeUserCredits(id string, credits int, now string) (model.User, bool, error) {
+	db, err := DB()
+	if err != nil {
+		return model.User{}, false, err
+	}
+	if credits <= 0 {
+		user, ok, err := GetUserByID(id)
+		return user, ok, err
+	}
+	tx := db.Model(&model.User{}).Where("id = ? AND credits >= ?", id, credits).Updates(map[string]any{
+		"credits":    gorm.Expr("credits - ?", credits),
+		"updated_at": now,
+	})
+	if tx.Error != nil {
+		return model.User{}, false, tx.Error
+	}
+	user, ok, err := GetUserByID(id)
+	return user, ok && tx.RowsAffected > 0, err
+}
+
 // SaveCreditLog 保存算力点变更流水。
 func SaveCreditLog(log model.CreditLog) (model.CreditLog, error) {
 	db, err := DB()