fix: 修复变量名冲突错误 CS0136

AssetManager.Services/PortfolioService.cs

@@ -375,19 +375,19 @@ public class PortfolioService : IPortfolioService
         if (request.type?.ToLower() == "sell")
         {
             // 校验是否有该持仓
-            var position = _db.Queryable<Position>()
+            var existingPosition = _db.Queryable<Position>()
                 .Where(pos => pos.PortfolioId == request.portfolioId && pos.StockCode == request.stockCode)
                 .First();
 
-            if (position == null)
+            if (existingPosition == null)
             {
                 throw new Exception($"该组合中不存在标的 {request.stockCode}，无法卖出");
             }
 
             // 校验卖出数量不超过持仓数量
-            if (request.amount > (double)position.Shares)
+            if (request.amount > (double)existingPosition.Shares)
             {
-                throw new Exception($"卖出数量不能超过持仓数量，当前持仓 {position.Shares} 份");
+                throw new Exception($"卖出数量不能超过持仓数量，当前持仓 {existingPosition.Shares} 份");
             }
         }