refactor(swap-test): 抽取 TestableSwapEodPositionService 公共基类收敛重复 Stub

- 新建 TestableSwapEodPositionService 收敛 8/8 Stub 重复的高频 override
  (PersistEodSwapPosition/SaveAllChanges/GetCurrencyRate/AddClientCash)
  + 统一 OptUserInfo 构造 + PersistedPositions/SaveChangesCount 输出捕获
- SwapEodPositionService.DealInterests 改 protected virtual（行为零变化）
- 8 个 ScenarioTest 改为继承基类，删除重复 override
- 消灭 DealInterestsScenarioTest/DealInterestsGoldenReplayTest 的反射调用
  (typeof().GetMethod().Invoke → 直接调用 DealInterests)

验证：dotnet build 0 错误；dotnet test SwapModule 284通过/6跳过/0失败

UnitTestProject/Modules/SwapModule/GLMS20260105GoldenTest.cs

@@ -212,10 +212,10 @@ namespace YLErp.Modules.SwapModule
 
         #region 回放用 Stub
 
-        private sealed class ReplayStubService : SwapEodPositionService
+        private sealed class ReplayStubService : TestableSwapEodPositionService
         {
             private readonly string _underlyingCode;
-            public ReplayStubService(string underlyingCode) : base(new OptUserInfo(0, "Replay", OptUserFrom.UnitTest))
+            public ReplayStubService(string underlyingCode) : base("Replay")
             {
                 _underlyingCode = underlyingCode;
             }
@@ -238,9 +238,6 @@ namespace YLErp.Modules.SwapModule
                 return 0m;
             }
 
-            protected override void SaveAllChanges() { }
-            protected override double GetCurrencyRate(string q, string s, DateTime d, bool p, CurrencyRateType t) => 1.0;
-
             public eod_swap_position ExecuteUpdateEodPosition(
                 swap_position swapPosition, eod_swap_position eod, trade td,
                 DateTime valueDate, DateTime preSettleDate, List<swap_flow_event> unwindEvents)