添加腾讯财经接口价格日志，方便排查当日盈亏为0问题

AssetManager.Infrastructure/Services/MarketDataService.cs

@@ -75,6 +75,9 @@ public class MarketDataService : IMarketDataService
             {
                 prevClose = currentPrice; // 解析失败用当前价当昨收
             }
+            
+            _logger.LogDebug("腾讯财经接口返回 {Symbol}：最新价 {CurrentPrice}，昨收价 {PrevClose}，涨跌额 {Change}", 
+                symbol, currentPrice, prevClose, currentPrice - prevClose);
 
             return new MarketPriceResponse
             {