feat(telegram): configure deploy status and error level logging notification via Telegram API

src/dotnet/QuantEngine.Web/Infrastructure/TelegramSink.cs

@@ -0,0 +1,56 @@
+using Serilog.Core;
+using Serilog.Events;
+using System.Net.Http;
+using System.Text;
+using System.Text.Json;
+
+namespace QuantEngine.Web.Infrastructure
+{
+    public class TelegramSink : ILogEventSink
+    {
+        private readonly string _botToken;
+        private readonly string _chatId;
+        private static readonly HttpClient HttpClient = new HttpClient();
+
+        public TelegramSink(string botToken, string chatId)
+        {
+            _botToken = botToken;
+            _chatId = chatId;
+        }
+
+        public void Emit(LogEvent logEvent)
+        {
+            if (logEvent.Level >= LogEventLevel.Error)
+            {
+                var sb = new StringBuilder();
+                sb.AppendLine("🚨 **QuantEngine Error Log**");
+                sb.AppendLine($"• Timestamp: {logEvent.Timestamp:yyyy-MM-dd HH:mm:ss}");
+                sb.AppendLine($"• Level: {logEvent.Level}");
+                sb.AppendLine($"• Message: {logEvent.RenderMessage()}");
+
+                if (logEvent.Exception != null)
+                {
+                    sb.AppendLine($"• Exception: {logEvent.Exception.Message}");
+                }
+
+                try
+                {
+                    var payload = new
+                    {
+                        chat_id = _chatId,
+                        text = sb.ToString(),
+                        parse_mode = "Markdown"
+                    };
+                    var content = new StringContent(JsonSerializer.Serialize(payload), Encoding.UTF8, "application/json");
+                    
+                    // Fire and forget to avoid blocking main execution threads
+                    _ = HttpClient.PostAsync($"https://api.telegram.org/bot{_botToken}/sendMessage", content);
+                }
+                catch
+                {
+                    // Fallback to avoid crash loops inside logger
+                }
+            }
+        }
+    }
+}