refactor(accrual): 拆分FundingLegAccrual→SimpleInterestAccrual/CompoundInterestAccrual

单利与复利语义完全不同(单利本金恒定/复利重置日并本金),
拆成两个独立静态类,各自只含自己的方法:

SimpleInterestAccrual:
- AccrueEod (原AccrueSimpleEod)
- AccruePeriod (原AccrueSimplePeriod)

CompoundInterestAccrual:
- EodBasis (原CompoundEodBasis)
- AccrueEod (原AccrueCompoundEod)
- AccruePeriod (原AccrueCompoundPeriod)

方法名去掉Simple/Compound前缀(类名已携带类型),消除冗余
SwapModule零回归(7基线/510通过)

UnitTestProject/Modules/SwapModule/Accrual/SimplePeriodShadowTest.cs

@@ -12,7 +12,7 @@ using YLErp.Derivatives.Interest;
 namespace UnitTestProject.Modules.SwapModule.Accrual
 {
     /// <summary>
-    /// 影子测试：CalcDailySimpleInterest（旧逐日循环）vs FundingLegAccrual.AccrueSimplePeriod（新分段纯函数）。
+    /// 影子测试：CalcDailySimpleInterest（旧逐日循环）vs SimpleInterestAccrual.AccruePeriod（新分段纯函数）。
     /// </summary>
     [TestClass]
     public class SimplePeriodShadowTest
@@ -106,7 +106,7 @@ namespace UnitTestProject.Modules.SwapModule.Accrual
             // 旧代码差分: dynomicPrincipal = preEod.TdInterestPrincipal(=0) + posiPrincipal - orginPv = 0
             var segRates = new List<(DateTime, decimal)> { (StartDate, Spread) };
             var accrualPrincipal = 0m + Notional - Notional; // 差分 = 0
-            var result = FundingLegAccrual.AccrueSimplePeriod(
+            var result = SimpleInterestAccrual.AccruePeriod(
                 priorAccrued: 0m,
                 notional: 0m,
                 unwindFraction: 1m,
@@ -152,7 +152,7 @@ namespace UnitTestProject.Modules.SwapModule.Accrual
             // 差分本金 = preEod.TdInterestPrincipal + posiPrincipal - orginPv
             var accrualPrincipal = Notional + Notional - Notional;
             var segRates = new List<(DateTime, decimal)> { (StartDate, Spread) };
-            var result = FundingLegAccrual.AccrueSimplePeriod(
+            var result = SimpleInterestAccrual.AccruePeriod(
                 priorAccrued: 200_000m * 0.5m,
                 notional: accrualPrincipal,
                 unwindFraction: 0.5m,
@@ -215,7 +215,7 @@ namespace UnitTestProject.Modules.SwapModule.Accrual
 
             // 差分本金 = preEod.TdInterestPrincipal + posiPrincipal - orginPv
             var accrualPrincipal = Notional + Notional - Notional;
-            var result = FundingLegAccrual.AccrueSimplePeriod(
+            var result = SimpleInterestAccrual.AccruePeriod(
                 priorAccrued: 200_000m * closePct,
                 notional: accrualPrincipal,
                 unwindFraction: closePct,