data 透传闭环：发货数据回显、回调带回，并限制 2KB

- 「查询发货数据」响应新增 data（下单透传原样回显，供自建发货页预填/展示）
- 回调 payload 带回 data（下单传 → 回调收，商户对接免回查）
- 创建订单 data 限制最长 2048 字节
- 文档更新：data 用途（自建页预填/回调/上游查单约定字段）、发货数据与回调示例
- 单测覆盖 data 回显

backend/internal/service/delivery.go

@@ -113,6 +113,7 @@ type DeliveryOrderInfo struct {
 	GameUID          string                 `json:"game_uid,omitempty"`
 	RoleName         string                 `json:"role_name,omitempty"`
 	PayScore         int                    `json:"pay_score,omitempty"`
+	Data             map[string]interface{} `json:"data,omitempty"`
 	Good             map[string]interface{} `json:"good,omitempty"`
 }
 
@@ -558,6 +559,7 @@ func (s *DeliveryService) buildDeliveryState(openOrder *OpenOrderQuery, order *m
 		GameUID:          openOrder.GameUID,
 		RoleName:         openOrder.RoleName,
 		PayScore:         openOrder.PayScore,
+		Data:             requestDataMap(order.RequestData),
 		Good:             good,
 	}
 	return info, order, goodID, nil
@@ -767,6 +769,7 @@ func (s *DeliveryService) prepareOrder(orderNo string, requireCanShip bool, auth
 		GameUID:          openOrder.GameUID,
 		RoleName:         openOrder.RoleName,
 		PayScore:         openOrder.PayScore,
+		Data:             requestDataMap(order.RequestData),
 		Good:             good,
 	}
 	return info, order, goodID, nil

backend/internal/service/delivery_test.go

@@ -221,6 +221,10 @@ func TestDeliveryMerchantApiBindAndSubmit(t *testing.T) {
 		APIClientID:   1,
 		ClientOrderNo: "delivery-api-001",
 		SKU:           "suit_alan_walker",
+		RequestData: map[string]interface{}{
+			"game_account": "4808146277",
+			"game_channel": "ios-wechat",
+		},
 	})
 	if err != nil {
 		t.Fatalf("create order: %v", err)
@@ -234,6 +238,9 @@ func TestDeliveryMerchantApiBindAndSubmit(t *testing.T) {
 	if !info.CanShip || info.Product == nil || info.Product.Image == "" {
 		t.Fatalf("merchant order should include delivery data: %+v", info)
 	}
+	if info.Data["game_account"] != "4808146277" || info.Data["game_channel"] != "ios-wechat" {
+		t.Fatalf("delivery order should echo request data: %+v", info.Data)
+	}
 
 	bind, err := deliverySvc.BindForMerchant(merchantID, created.Order.OrderNo, "4808146277")
 	if err != nil {

backend/internal/service/fulfillment.go

@@ -772,7 +772,7 @@ func CanFulfill(order *model.FulfillmentOrder) (bool, string) {
 
 func orderCallbackData(order *model.FulfillmentOrder) map[string]interface{} {
 	canShip, cannotShipReason := CanFulfill(order)
-	return map[string]interface{}{
+	data := map[string]interface{}{
 		"order_no":           order.OrderNo,
 		"client_order_no":    order.ClientOrderNo,
 		"product_sku":        order.ProductSKU,
@@ -788,6 +788,10 @@ func orderCallbackData(order *model.FulfillmentOrder) map[string]interface{} {
 		"provider_order_no":  order.ProviderOrderNo,
 		"failure_reason":     order.FailureReason,
 	}
+	if requestData := requestDataMap(order.RequestData); len(requestData) > 0 {
+		data["data"] = requestData
+	}
+	return data
 }
 
 // ----- 仪表盘统计 -----
@@ -1309,6 +1313,15 @@ func resultDataMap(raw string) map[string]interface{} {
 	return m
 }
 
+// requestDataMap 解析下单透传的 data（RequestData），非法或为空时返回空 map。
+func requestDataMap(raw string) map[string]interface{} {
+	m := map[string]interface{}{}
+	if raw != "" && json.Valid([]byte(raw)) {
+		_ = json.Unmarshal([]byte(raw), &m)
+	}
+	return m
+}
+
 func resultDataString(raw, key string) string {
 	if v, ok := resultDataMap(raw)[key].(string); ok {
 		return v