fix: send Telegram deployment notification asynchronously

- Move deployment completion alert to background Task
- Prevent blocking app startup waiting for Telegram API
- Fixes 'service not responding' errors during health check
- Add error handling for Telegram send failures

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

TaxBaik.Web/Program.cs

@@ -231,22 +231,34 @@ try
 {
     Log.Information("애플리케이션 시작: {Environment}", app.Environment.EnvironmentName);
     if (!app.Environment.IsDevelopment())
+    {
+        // 배포 완료 알림을 백그라운드에서 비동기 전송 (앱 시작 블록 방지)
+        _ = Task.Run(async () =>
+        {
+            try
             {
                 using (var scope = app.Services.CreateScope())
                 {
                     var telegramService = scope.ServiceProvider.GetRequiredService<ITelegramNotificationService>();
-            // 배포 완료 알림
                     await telegramService.SendInfoAsync(
                         "✅ 배포 완료",
                         $"환경: {app.Environment.EnvironmentName}\n상태: 정상 운영 중");
                 }
             }
+            catch (Exception ex)
+            {
+                Log.Error(ex, "배포 완료 알림 전송 실패");
+            }
+        });
+    }
     app.Run();
 }
 catch (Exception ex)
 {
     Log.Fatal(ex, "애플리케이션 강종");
     if (!app.Environment.IsDevelopment())
+    {
+        try
         {
             using (var scope = app.Services.CreateScope())
             {
@@ -256,6 +268,11 @@ catch (Exception ex)
                     $"환경: {app.Environment.EnvironmentName}\n오류: {ex.Message}");
             }
         }
+        catch (Exception telegramEx)
+        {
+            Log.Error(telegramEx, "오류 알림 전송 실패");
+        }
+    }
     throw;
 }
 finally