feat(dotnet): migrate core formulas, deploy tools, and blazor admin web app to .NET 10

src/dotnet/QuantEngine.Infrastructure/External/YahooFinanceClient.cs

@@ -0,0 +1,30 @@
+using System;
+using System.Net.Http;
+using System.Threading.Tasks;
+using QuantEngine.Core.Interfaces;
+
+namespace QuantEngine.Infrastructure.External
+{
+    public class YahooFinanceClient : IYahooFinanceClient
+    {
+        private readonly HttpClient _httpClient;
+        private const string UserAgent = "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/126.0 Safari/537.36";
+
+        public YahooFinanceClient(HttpClient httpClient)
+        {
+            _httpClient = httpClient;
+        }
+
+        public async Task<string> FetchHistoricalDataAsync(string symbol, string range = "4mo", string interval = "1d")
+        {
+            var url = $"https://query1.finance.yahoo.com/v8/finance/chart/{symbol}?range={range}&interval={interval}";
+            using var request = new HttpRequestMessage(HttpMethod.Get, url);
+            request.Headers.Add("User-Agent", UserAgent);
+
+            var response = await _httpClient.SendAsync(request);
+            response.EnsureSuccessStatusCode();
+
+            return await response.Content.ReadAsStringAsync();
+        }
+    }
+}