拆分 service 与前端大文件,修复 CORS 配置与格式问题

- 后端 internal/service 按职责拆分:
  fulfillment.go(1397→527)拆出 wallet/timeout/data/order/query/dashboard/shipnotify
  delivery.go(1124→801)拆出 upstream/link/state/helpers
  merchant.go(855→251)拆出 member/product/api_client/catalog/helpers
- 前端 MerchantCenter.tsx(1327→606)拆出 merchantCenterTabs/merchantCenterUtils
- docker-compose backend 透传 CORS_ALLOWED_ORIGINS
- CORS 白名单实现(config/router/README/.env.example 配套)
- 修复 gofmt 与文件尾部多余空行

backend/internal/service/fulfillment_order.go

@@ -0,0 +1,45 @@
+package service
+
+import (
+	"errors"
+	"math"
+	"strings"
+
+	"affiliate_dash/internal/model"
+	"affiliate_dash/internal/pkg/timeutil"
+
+	"github.com/google/uuid"
+)
+
+func newFulfillmentOrderNo() string {
+	return "FO" + timeutil.Now().Format(timeutil.OrderNoLayout) + strings.ReplaceAll(uuid.NewString()[:12], "-", "")
+}
+
+func newTestFulfillmentOrderNo() string {
+	return "O" + timeutil.Now().Format(timeutil.OrderNoLayout) + strings.ReplaceAll(uuid.NewString()[:12], "-", "")
+}
+
+// calculateServiceFee 按"百分比或固定"二选一计算手续费：
+//   - feeType=rate：按 baseAmount * feeRateBP / 10000 计算
+//   - feeType=fixed：直接取 feeFixedAmount
+//
+// 二者互斥，不会叠加。
+func calculateServiceFee(baseAmount int64, feeType string, feeRateBP, feeFixedAmount int64) (int64, error) {
+	if baseAmount < 0 || feeRateBP < 0 || feeFixedAmount < 0 {
+		return 0, errors.New("订单金额或手续费配置无效")
+	}
+	switch feeType {
+	case model.FeeTypeFixed:
+		return feeFixedAmount, nil
+	case model.FeeTypeRate, "":
+		if feeRateBP > 10000 {
+			return 0, errors.New("手续费比例不能超过 10000 BP")
+		}
+		if feeRateBP > 0 && baseAmount > math.MaxInt64/feeRateBP {
+			return 0, errors.New("手续费金额超出范围")
+		}
+		return baseAmount * feeRateBP / 10000, nil
+	default:
+		return 0, errors.New("无效的手续费类型")
+	}
+}