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/delivery_helpers.go

@@ -0,0 +1,77 @@
+package service
+
+import (
+	"fmt"
+	"strings"
+)
+
+func buildDeliveryProduct(openProduct *OpenOrderProduct, good map[string]interface{}) *DeliveryProduct {
+	if openProduct == nil {
+		return nil
+	}
+	product := &DeliveryProduct{
+		Name: openProduct.Name,
+		SKU:  openProduct.SKU,
+		Game: openProduct.Game,
+	}
+	if title := stringFromMap(good, "title"); title != "" {
+		product.Name = title
+	}
+	product.Image = stringFromMap(good, "image")
+	return product
+}
+
+func isZeroCode(code interface{}) bool {
+	switch v := code.(type) {
+	case nil:
+		return true
+	case float64:
+		return v == 0
+	case string:
+		return v == "0"
+	default:
+		return false
+	}
+}
+
+func stringFromMap(m map[string]interface{}, key string) string {
+	if m == nil {
+		return ""
+	}
+	switch v := m[key].(type) {
+	case string:
+		return v
+	case float64:
+		return fmt.Sprintf("%.0f", v)
+	default:
+		if v != nil {
+			return fmt.Sprint(v)
+		}
+		return ""
+	}
+}
+
+func firstNonEmpty(values ...string) string {
+	for _, value := range values {
+		if strings.TrimSpace(value) != "" {
+			return strings.TrimSpace(value)
+		}
+	}
+	return ""
+}
+
+func gameChannelText(account map[string]interface{}) string {
+	area := stringFromMap(account, "game_account_area")
+	plat := stringFromMap(account, "game_account_plat")
+	if area == "" && plat == "" {
+		return ""
+	}
+	return strings.Trim(strings.Join([]string{area, plat}, "-"), "-")
+}
+
+func truncateDeliveryText(value string) string {
+	if len(value) <= 300 {
+		return value
+	}
+	return value[:300]
+}