refactor(swap): 提取 SwapPositionQueries.ActiveByTrade 收口有效持仓查询

- 新增 SwapPositionQueries.ActiveByTrade 静态扩展，收口 'SwapTradeId==X && !Invalid' 规则到单一真相
- 替换 SwapDealService/SwapEodPositionService/SwapTradeService 共 7 处纯重复谓词
- 仅返回 IQueryable，不调 SaveChanges，不动 FindTrade seam / 事务边界；行为保持等价

YLErpDAL/Modules/SwapModule/SwapTradeService.cs

@@ -1188,7 +1188,7 @@ namespace YLErp.Modules.SwapModule
                 tradeObj.trade_Initial_Margin = new trade_initial_margin();
             }
             tradeObj.trade_extend = DbContext.trade_extend.FirstOrDefault(x => x.TradeId == intid);
-            tradeObj.swap_positions = DbContext.swap_position.Where(x => x.SwapTradeId == intid && !x.Invalid).ToList();
+            tradeObj.swap_positions = DbContext.swap_position.ActiveByTrade(intid).ToList();
             tradeObj.swap_positions = tradeObj.swap_positions.Where(x => x.PosiQuantity > 0 || x.InterestDirection > 0).ToList();
             var intervalPositions = tradeObj.swap_positions.Where(x => string.IsNullOrEmpty(x.UnderlyingCode) && x.IsInitial).ToList();
             var intervalPositionIds = intervalPositions.Select(s => s.id).ToList();
@@ -1517,7 +1517,7 @@ namespace YLErp.Modules.SwapModule
                 throw new ServiceException("交易不存在");
             }
             bool backToBegin = td.TradeDate == valueDate;
-            var swapPositions = DbContext.swap_position.Where(x => x.SwapTradeId == tradeId && !x.Invalid).ToList();
+            var swapPositions = DbContext.swap_position.ActiveByTrade(tradeId).ToList();
             td.trade_extend = DbContext.trade_extend.FirstOrDefault(x => x.TradeId == td.id);
            
             //展期