支持 GroupCost 属性并修复计算逻辑错误

在 FinancialController.cs 中新增对 GroupCost 属性的处理逻辑，确保在多个代码块中正确赋值。
修复 Grp_GroupCostParameter.cs 中 otherSinglePrice 的计算逻辑错误，移除多余的加号。
在 Fin_ForeignReceivablesView.cs 中新增 GroupCost 属性，支持前端或其他模块对该数据的访问。

OASystem/OASystem.Api/Controllers/FinancialController.cs

@@ -2786,6 +2786,7 @@ namespace OASystem.API.Controllers
                             ReceivedTotal = item.receivedTotal,
                             Balance = item.balPrice,
                             Collection = item.schedule,
+                            GroupCost = item.groupCost.ToString("#0.00"),
                         };
                         excNo++;
                         DateTime time = Convert.ToDateTime(item.visitDate);
@@ -2848,6 +2849,7 @@ namespace OASystem.API.Controllers
                             ClientUnit = item.clientUnit,
                             VisitDate = item.visitDate,
                             ChangeColorLabel = item.ChangeColorLabel,
+                            GroupCost = item.groupCost.ToString("#0.00")
                         };
                         excNo1++;
                         list_Ex_Orange.Add(exc);
@@ -2861,6 +2863,7 @@ namespace OASystem.API.Controllers
                             ClientUnit = item.clientUnit,
                             VisitDate = item.visitDate,
                             ChangeColorLabel = item.ChangeColorLabel,
+                            GroupCost = item.groupCost.ToString("#0.00")
                         };
                         excNo2++;
                         list_Ex_Red.Add(exc);

OASystem/OASystem.Domain/Entities/Groups/Grp_GroupCostParameter.cs

@@ -387,7 +387,8 @@
             get
             {
                 var list = new List<ChildFeeInfo>();
-                var otherSinglePrice = VisaSinglePrice + PolicySinglePrice + TicketSinglePrice + FerryTicketSinglePrice + NucleicAcidTesSinglePrice + GroundSinglePrice + BusinessActivitySinglePrice + PettyCashSinglePrice;
+                var otherSinglePrice = VisaSinglePrice + PolicySinglePrice + TicketSinglePrice + FerryTicketSinglePrice + 
+                    NucleicAcidTesSinglePrice + GroundSinglePrice + BusinessActivitySinglePrice + PettyCashSinglePrice;
                 //经济舱 TBR、经济舱 SGR、经济舱 JS/ES、经济舱 SUITE、公务舱 TBR、公务舱 SGR、公务舱 JS/ES、公务舱 SUITE、头等舱 JS/ES、头等舱 SUITE
                 if (JJCRS > 0)
                 {

OASystem/OASystem.Domain/ViewModels/Financial/Fin_ForeignReceivablesView.cs

@@ -317,6 +317,8 @@ namespace OASystem.Domain.ViewModels.Financial
         public string Sign { get; set; }
 
         public string ChangeColorLabel { get; set; }
+
+        public string GroupCost { get; set; }
     }
 
     public class PostSyntheticalReceivableByDateRangeResultView