refactor(shipment): 修改Gen方法返回值类型

- 将Gen方法的返回值从error修改为(mixedId int64, err error)
- 更新错误处理逻辑以返回新的返回值结构
- 修改客户端调用方式以适配新的返回值格式

erp/shipment/mixed.go

@@ -49,11 +49,11 @@ type ArgsMixedGen struct {
 }
 
 // Gen @TITLE 生成
-func (m *mixed) Gen(ctx context.Context, args ArgsMixedGen) error {
+func (m *mixed) Gen(ctx context.Context, args ArgsMixedGen) (mixedId int64, err error) {
 	xClient, err := client.GetClient(m)
 	if err != nil {
-		return err
+		return mixedId, err
 	}
-	reply := 0
+	err = xClient.Call(ctx, "Gen", args, &mixedId)
-	return xClient.Call(ctx, "Gen", args, &reply)
+	return
 }