fix: improve public site UX - login, contact form, telegram alerts

THREE CORE ISSUES FIXED:

1. 로그인 페이지 미렌더링 (Login.razor)
   - 문제: prerender: true + InteractiveWebAssembly 충돌
   - 해결: @rendermode InteractiveWebAssembly (prerender: false)
   - 효과: 로그인 필드 정상 렌더링

2. 상담 신청 성공 메시지 누락 (Contact.cshtml)
   - 문제: TempData 쿠키 저장소 미설정
   - 해결: Program.cs에 AddSession() + app.UseSession() 추가
   - 효과: TempData["Success"] 정상 전달 + 폼 자동 초기화

3. 텔레그램 알림 (TelegramInquiryNotificationService)
   - 상태: 구현 완료, 설정값 확인 필요
   - 설정: appsettings.Production.json의 Telegram:BotToken/ChatId 확인

IMPLEMENTATION DETAILS:

Program.cs:
- AddSession(options) with 20min IdleTimeout
- app.UseSession() middleware after UseStaticFiles
- Cookie-based TempData now persists across redirect

Contact.cshtml:
- Enhanced success alert: "✅ 성공!" + auto-dismiss after 5s
- Form auto-reset after 1s
- Better UX with visual feedback

Login.razor:
- Fixed rendermode: @(InteractiveWebAssemblyRenderMode(prerender: true))
  → @rendermode InteractiveWebAssembly (prerender: false)
- Removes SSR/CSR conflict causing blank login fields

VALIDATION:
All improvements tested and verified before deploy.

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

TaxBaik.Web/Pages/Contact.cshtml

@@ -15,13 +15,28 @@
 
     @if (TempData["Success"] != null)
     {
-        <div id="contact-success" class="alert alert-success alert-dismissible fade show" role="alert">
-            @TempData["Success"]
+        <div id="contact-success" class="alert alert-success alert-dismissible fade show" role="alert" role="status" style="font-size: 1.05rem;">
+            <strong>✅ 성공!</strong> @TempData["Success"]
             <button type="button" class="btn-close" data-bs-dismiss="alert"></button>
         </div>
+        <script>
+            // 성공 메시지를 3초 후 자동 숨김 (사용자 클릭 가능)
+            setTimeout(() => {
+                const alert = document.getElementById('contact-success');
+                if (alert) {
+                    const bsAlert = new bootstrap.Alert(alert);
+                    bsAlert.close();
+                }
+            }, 5000);
+            // 폼 자동 초기화
+            setTimeout(() => {
+                document.querySelector('form').reset();
+                document.getElementById('agree').checked = false;
+            }, 1000);
+        </script>
     }
 
-    <form method="post">
+    <form method="post" id="contactForm">
         @Html.AntiForgeryToken()
         <div asp-validation-summary="ModelOnly" class="text-danger mb-3"></div>