refactor(ai): 重构AI接口算力点扣费逻辑并添加失败返还机制

- 移除预检查算力点步骤，改为请求前预扣算力点
- 添加请求失败时自动返还算力点的功能
- 修改copyAIResponse函数参数以支持失败回调处理
- 在响应状态异常时也执行算力点返还操作
- 从auth服务中移除EnsureUserCredits方法
- 新增RefundUserCredits方法用于返还用户算力点
- 添加AI_REFUND算力点日志类型常量
- 更新算力点日志类型说明及展示标签

repository/user.go

@@ -79,11 +79,6 @@ 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 {
@@ -104,6 +99,26 @@ func ConsumeUserCredits(id string, credits int, now string) (model.User, bool, e
 	return user, ok && tx.RowsAffected > 0, err
 }
 
+func RefundUserCredits(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 = ?", id).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()