fix: 支付回调补写 actual_paid_amount 字段，从支付平台回调中提取实付金额

- HandlePaymentCallback 新增 actualPaidAmount int64 参数，Updates 写入 actual_paid_amount
- 微信 V2 回调从 TotalFee 字符串解析分值；V3 直接使用 TotalAmount
- 支付宝回调优先取 buyer_pay_amount（实付），回退 total_amount，元转分使用 math.Round
- 富友回调从 OrderAmt 字符串解析分值
- dispatchWechatCallback 同步增加 paidAmount 参数透传

internal/handler/callback/payment.go

@@ -3,7 +3,9 @@ package callback
 import (
 	"context"
 	"fmt"
+	"math"
 	"net/http"
+	"strconv"
 	"strings"
 
 	"github.com/gofiber/fiber/v2"
@@ -97,7 +99,9 @@ func (h *PaymentHandler) WechatPayCallback(c *fiber.Ctx) error {
 		if result.TradeState != "SUCCESS" {
 			return h.wechatV2SuccessResponse(c)
 		}
-		if err := h.dispatchWechatCallback(ctx, result.OutTradeNo, result.TransactionID); err != nil {
+		// TotalFee 为字符串格式的分，解析失败则降级为 0（后续 handlePaymentCallback 会记录日志）
+		totalFee, _ := strconv.ParseInt(result.TotalFee, 10, 64)
+		if err := h.dispatchWechatCallback(ctx, result.OutTradeNo, result.TransactionID, totalFee); err != nil {
 			return errors.Wrap(errors.CodeWechatCallbackInvalid, err, "处理微信支付回调失败")
 		}
 
@@ -111,7 +115,7 @@ func (h *PaymentHandler) WechatPayCallback(c *fiber.Ctx) error {
 			if result.TradeState != "SUCCESS" {
 				return nil
 			}
-			return h.dispatchWechatCallback(ctx, result.OutTradeNo, result.TransactionID)
+			return h.dispatchWechatCallback(ctx, result.OutTradeNo, result.TransactionID, result.TotalAmount)
 		})
 		if err != nil {
 			return errors.Wrap(errors.CodeWechatCallbackInvalid, err, "处理微信支付回调失败")
@@ -125,10 +129,10 @@ func (h *PaymentHandler) WechatPayCallback(c *fiber.Ctx) error {
 }
 
 // dispatchWechatCallback 按订单号前缀将支付结果分发到对应业务
-func (h *PaymentHandler) dispatchWechatCallback(ctx context.Context, outTradeNo, transactionID string) error {
+func (h *PaymentHandler) dispatchWechatCallback(ctx context.Context, outTradeNo, transactionID string, paidAmount int64) error {
 	switch {
 	case strings.HasPrefix(outTradeNo, "ORD"):
-		return h.orderService.HandlePaymentCallback(ctx, outTradeNo, model.PaymentMethodWechat)
+		return h.orderService.HandlePaymentCallback(ctx, outTradeNo, model.PaymentMethodWechat, paidAmount)
 	case strings.HasPrefix(outTradeNo, constants.AssetRechargeOrderPrefix):
 		if h.rechargeOrderService != nil {
 			return h.rechargeOrderService.HandlePaymentCallback(ctx, outTradeNo, model.PaymentByWechat, transactionID)
@@ -151,8 +155,24 @@ func (h *PaymentHandler) wechatV2SuccessResponse(c *fiber.Ctx) error {
 	return c.SendString(`<xml><return_code><![CDATA[SUCCESS]]></return_code><return_msg><![CDATA[OK]]></return_msg></xml>`)
 }
 
+// parseYuanToFen 将支付宝元为单位的金额字符串转换为分
+// 支付宝回调金额字段（buyer_pay_amount / total_amount）为字符串格式的元，如 "2.00"
+// 使用 math.Round 避免浮点运算精度误差
+func parseYuanToFen(yuan string) int64 {
+	if yuan == "" {
+		return 0
+	}
+	f, err := strconv.ParseFloat(yuan, 64)
+	if err != nil {
+		return 0
+	}
+	return int64(math.Round(f * 100))
+}
+
 type AlipayCallbackRequest struct {
-	OrderNo string `json:"out_trade_no" form:"out_trade_no"`
+	OrderNo        string `json:"out_trade_no" form:"out_trade_no"`
+	BuyerPayAmount string `json:"buyer_pay_amount" form:"buyer_pay_amount"`
+	TotalAmount    string `json:"total_amount" form:"total_amount"`
 }
 
 // AlipayCallback 支付宝回调
@@ -169,10 +189,17 @@ func (h *PaymentHandler) AlipayCallback(c *fiber.Ctx) error {
 
 	ctx := c.UserContext()
 
+	// 优先取 buyer_pay_amount（买家实付，扣除优惠券后），回退到 total_amount
+	rawAmount := req.BuyerPayAmount
+	if rawAmount == "" {
+		rawAmount = req.TotalAmount
+	}
+	paidAmount := parseYuanToFen(rawAmount)
+
 	// 按订单号前缀分发
 	switch {
 	case strings.HasPrefix(req.OrderNo, "ORD"):
-		if err := h.orderService.HandlePaymentCallback(ctx, req.OrderNo, model.PaymentMethodAlipay); err != nil {
+		if err := h.orderService.HandlePaymentCallback(ctx, req.OrderNo, model.PaymentMethodAlipay, paidAmount); err != nil {
 			return err
 		}
 	case strings.HasPrefix(req.OrderNo, constants.AssetRechargeOrderPrefix):
@@ -248,9 +275,11 @@ func (h *PaymentHandler) FuiouPayCallback(c *fiber.Ctx) error {
 	}
 
 	orderNo := notify.MchntOrderNo
+	// OrderAmt 为字符串格式的分，解析失败则降级为 0
+	orderAmt, _ := strconv.ParseInt(notify.OrderAmt, 10, 64)
 	switch {
 	case strings.HasPrefix(orderNo, "ORD"):
-		if err := h.orderService.HandlePaymentCallback(ctx, orderNo, "fuiou"); err != nil {
+		if err := h.orderService.HandlePaymentCallback(ctx, orderNo, "fuiou", orderAmt); err != nil {
 			return c.Send(fuiou.BuildNotifyFailResponse(err.Error()))
 		}
 	case strings.HasPrefix(orderNo, constants.AssetRechargeOrderPrefix):

internal/service/order/service.go

@@ -1410,7 +1410,7 @@ func (s *Service) WalletPay(ctx context.Context, orderID uint, buyerType string,
 	return nil
 }
 
-func (s *Service) HandlePaymentCallback(ctx context.Context, orderNo string, paymentMethod string) error {
+func (s *Service) HandlePaymentCallback(ctx context.Context, orderNo string, paymentMethod string, actualPaidAmount int64) error {
 	order, err := s.orderStore.GetByOrderNo(ctx, orderNo)
 	if err != nil {
 		if err == gorm.ErrRecordNotFound {
@@ -1424,10 +1424,11 @@ func (s *Service) HandlePaymentCallback(ctx context.Context, orderNo string, pay
 		result := tx.Model(&model.Order{}).
 			Where("id = ? AND payment_status = ?", order.ID, model.PaymentStatusPending).
 			Updates(map[string]any{
-				"payment_status": model.PaymentStatusPaid,
-				"payment_method": paymentMethod,
-				"paid_at":        now,
-				"expires_at":     nil, // 支付成功，清除过期时间
+				"payment_status":     model.PaymentStatusPaid,
+				"payment_method":     paymentMethod,
+				"paid_at":            now,
+				"expires_at":         nil, // 支付成功，清除过期时间
+				"actual_paid_amount": actualPaidAmount,
 			})
 		if result.Error != nil {
 			return errors.Wrap(errors.CodeDatabaseError, result.Error, "更新订单支付状态失败")