fix: 防止价格获取并发竞态条件

问题：多个并发请求同时获取同一股票价格，导致：
1. 外部 API 被重复调用（可能被限流）
2. 部分请求失败导致收益率显示 0%

解决方案：
- 使用 ConcurrentDictionary 存储进行中的请求
- GetOrAdd 模式确保同一时间只有一个请求在获取价格
- 其他并发请求等待第一个请求的结果
- 请求完成后移除 pending 任务

AssetManager.Infrastructure/Services/MarketDataService.cs

@@ -2,6 +2,7 @@ using AssetManager.Data;
 using AssetManager.Data.Repositories;
 using AssetManager.Models.DTOs;
 using Microsoft.Extensions.Logging;
+using System.Collections.Concurrent;
 
 namespace AssetManager.Infrastructure.Services;
 
@@ -20,6 +21,9 @@ public class MarketDataService : IMarketDataService
     private readonly ITiingoMarketService _tiingoService;
     private readonly IOkxMarketService _okxService;
     private readonly IMarketDataRepository _marketDataRepo;
+    
+    // 防止并发请求同一股票
+    private readonly ConcurrentDictionary<string, Task<MarketPriceResponse>> _pendingPriceRequests = new();
 
     public MarketDataService(
         ILogger<MarketDataService> logger,
@@ -39,9 +43,11 @@ public class MarketDataService : IMarketDataService
 
     /// <summary>
     /// 获取实时价格（自动根据资产类型路由到对应数据源）
+    /// 使用并发控制防止重复请求
     /// </summary>
     public async Task<MarketPriceResponse> GetPriceAsync(string symbol, string assetType)
     {
+        var cacheKey = $"{symbol.ToUpper()}_{assetType.ToUpper()}";
         _logger.LogInformation("获取实时价格: {Symbol}, 资产类型: {AssetType}", symbol, assetType);
         
         // 先查缓存
@@ -60,7 +66,27 @@ public class MarketDataService : IMarketDataService
             };
         }
 
-        // 缓存未命中，调用API
+        // 使用 GetOrAdd 模式防止并发重复请求
+        var priceTask = _pendingPriceRequests.GetOrAdd(cacheKey, _ => FetchPriceFromSourceAsync(symbol, assetType));
+        
+        try
+        {
+            return await priceTask;
+        }
+        finally
+        {
+            // 请求完成后移除（无论成功失败）
+            _pendingPriceRequests.TryRemove(cacheKey, out _);
+        }
+    }
+
+    /// <summary>
+    /// 从数据源获取价格（内部方法）
+    /// </summary>
+    private async Task<MarketPriceResponse> FetchPriceFromSourceAsync(string symbol, string assetType)
+    {
+        _logger.LogInformation("从数据源获取价格: {Symbol}, 资产类型: {AssetType}", symbol, assetType);
+        
         MarketPriceResponse response;
         string source;
         

AssetManager.Services/PortfolioService.cs

@@ -657,15 +657,15 @@ public class PortfolioService : IPortfolioService
         {
             if (DateTime.TryParse(request.TransactionDate, out var parsedDate))
             {
-                // 如果只传了日期，时间部分默认用当前时间
+                transactionTime = parsedDate.Date;
-                transactionTime = parsedDate.Date + DateTime.Now.TimeOfDay;
             }
         }
-        else if (!string.IsNullOrEmpty(request.TransactionTime))
+        // 组合时间部分
+        if (!string.IsNullOrEmpty(request.TransactionTime))
         {
-            if (DateTime.TryParse(request.TransactionTime, out var parsedTime))
+            if (TimeSpan.TryParse(request.TransactionTime, out var parsedTime))
             {
-                transactionTime = parsedTime;
+                transactionTime = transactionTime.Date + parsedTime;
             }
         }
 
@@ -821,12 +821,16 @@ public class PortfolioService : IPortfolioService
         request.PortfolioId = portfolioId;
         var response = await CreateTransaction(request, userId);
         
+        // 使用实际交易时间
+        var transactionDate = request.TransactionDate ?? DateTime.Now.ToString("yyyy-MM-dd");
+        var transactionTime = request.TransactionTime ?? DateTime.Now.ToString("HH:mm");
+        
         return new TransactionItem
         {
             Id = response.Id,
             PortfolioId = portfolioId,
-            Date = DateTime.Now.ToString("yyyy-MM-dd"),
+            Date = transactionDate,
-            Time = DateTime.Now.ToString("HH:mm:ss"),
+            Time = transactionTime,
             Type = request.Type,
             StockCode = request.StockCode,
             Amount = response.TotalAmount,