fix: 富友订单支持退款，0 元退款不强制客户收款材料映射

- decideRefundMethods 将 fuiou 与 wechat、alipay 按线上支付处理，修复富友订单报"该订单的支付方式不支持退款"
- 客户收款信息退款仅在金额大于 0 时强制映射并提交客户收款信息与凭证；0 元退款允许客户收款信息为空

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/application/wecom/scene.go

@@ -6,6 +6,7 @@ import (
 	"encoding/hex"
 	stdErrors "errors"
 	"fmt"
+	"strconv"
 	"strings"
 	"time"
 
@@ -332,6 +333,7 @@ func RequiredSceneFields(businessType string) []RequiredSceneField {
 }
 
 // RequiredRefundFields 返回退款提交固定与条件必需字段；快照方式编码缺失或未知时由表单构建拒绝。
+// 客户收款信息退款要求客户收款信息与凭证必须映射并提交；0 元退款不退钱，两者不强制。
 func RequiredRefundFields(snapshot map[string]any) []RequiredSceneField {
 	methodCode, ok := snapshot[constants.ApprovalFieldRefundMethodCode].(string)
 	methodCode = strings.TrimSpace(methodCode)
@@ -339,12 +341,22 @@ func RequiredRefundFields(snapshot map[string]any) []RequiredSceneField {
 		return []RequiredSceneField{{Code: constants.ApprovalFieldRefundMethodCode, Name: "退款方式编码"}}
 	}
 	result := []RequiredSceneField{{Code: constants.ApprovalFieldRefundMethod, Name: "退款方式", RequiredMapping: true}}
-	if methodCode == constants.RefundMethodCustomerAccount {
+	if methodCode == constants.RefundMethodCustomerAccount && !isZeroAmountRefund(snapshot) {
 		result = append(result, RequiredSceneField{Code: constants.ApprovalFieldCustomerAccountInfo, Name: "客户收款信息"}, RequiredSceneField{Code: constants.ApprovalFieldCustomerVoucherKey, Name: "客户收款凭证"})
 	}
 	return result
 }
 
+// isZeroAmountRefund 判断快照中的申请退款金额是否为 0；金额缺失或无法解析时按非 0 处理，保持强制校验。
+func isZeroAmountRefund(snapshot map[string]any) bool {
+	raw, ok := snapshot[constants.ApprovalFieldRequestedRefundAmount].(string)
+	if !ok {
+		return false
+	}
+	amount, err := strconv.ParseFloat(strings.TrimSpace(raw), 64)
+	return err == nil && amount == 0
+}
+
 // approvalBusinessTypes 返回全部已登记审批业务场景，供只读字段汇总复用。
 func approvalBusinessTypes() []string {
 	return []string{

internal/infrastructure/wecom/approval_form.go

@@ -101,7 +101,7 @@ func buildApprovalForm(ctx context.Context, businessType string, applicationID,
 	attachmentCount := 0
 	for _, mapping := range mappings {
 		raw, exists := lookupSnapshotValue(snapshot, mapping.BusinessField)
-		if !exists || raw == nil || isEmptyFileValue(mapping, raw) {
+		if !exists || raw == nil || isEmptyFileValue(mapping, raw) || isEmptyCustomerAccountInfo(mapping, raw) {
 			if requiredControls[mapping.ControlID] {
 				return approvalFormBuildResult{}, errors.New(errors.CodeInvalidStatus, "审批业务快照缺少模板必填字段: "+mapping.BusinessField)
 			}
@@ -142,6 +142,15 @@ func isEmptyFileValue(mapping dto.WeComControlMappingItem, raw any) bool {
 	}
 }
 
+// isEmptyCustomerAccountInfo 判断客户收款信息是否为空文本；只有 0 元退款可能为空，按未填写处理，由模板必填规则决定是否拦截。
+func isEmptyCustomerAccountInfo(mapping dto.WeComControlMappingItem, raw any) bool {
+	if strings.TrimSpace(mapping.BusinessField) != constants.ApprovalFieldCustomerAccountInfo {
+		return false
+	}
+	value, ok := raw.(string)
+	return ok && strings.TrimSpace(value) == ""
+}
+
 // lookupSnapshotValue 支持用点分路径读取嵌套业务快照，避免模板映射绑定具体 DTO。
 func lookupSnapshotValue(snapshot map[string]any, path string) (any, bool) {
 	segments := strings.Split(strings.TrimSpace(path), ".")

internal/service/refund/method.go

@@ -45,7 +45,8 @@ func (s *Service) decideRefundMethods(ctx context.Context, order *model.Order) (
 
 	decision := &refundMethodDecision{}
 	switch order.PaymentMethod {
-	case model.PaymentMethodWechat, model.PaymentMethodAlipay:
+	// 富友是微信支付的上游通道，套餐订单回调写入 fuiou，按线上支付处理。
+	case model.PaymentMethodWechat, model.PaymentMethodAlipay, model.ProviderTypeFuiou:
 		payment, err := s.loadPaidPackagePayment(ctx, order.ID)
 		if err != nil {
 			return nil, err