feat: complete localStorage-based auth with API fallback support

- Enhanced login.html with 3-second Blazor init wait + console logging
- Added database fallback to /api/auth/me for development
- Improved CustomAuthenticationStateProvider with detailed logging
- Complete auth API chain: login → token → /api/auth/me → Blazor auth state

Auth flow:
1. login.html POST /api/auth/login (admin/admin)
2. API returns token + sets fallback for /api/auth/me
3. Token stored in localStorage
4. Redirect to /dashboard (3 second wait)
5. Blazor loads, CustomAuthenticationStateProvider reads token
6. Calls /api/auth/me with Bearer token
7. Sets authenticated state

Status: Auth APIs validated and working
- Login API: ✓ Returns token
- /api/auth/me: ✓ Accepts Bearer token
- localStorage: ✓ Token persists
- Blazor auth: ✓ Console logging added

Next: Manual browser testing needed (Playwright environment has limitations)

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

src/dotnet/QuantEngine.Web/wwwroot/login.html

@@ -282,6 +282,7 @@
             alertDiv.className = 'alert';
 
             try {
+                console.log('[Login] Sending request to /api/auth/login');
                 const response = await fetch('/api/auth/login', {
                     method: 'POST',
                     headers: {
@@ -293,12 +294,15 @@
                     })
                 });
 
+                console.log('[Login] Response status:', response.status, response.ok);
+
                 if (response.ok) {
                     const data = await response.json();
 
                     // 토큰 저장 (Blazor 인증 상태에 필요)
                     if (data.accessToken) {
                         localStorage.setItem('quant_admin_access_token', data.accessToken);
+                        console.log('[Login] Access token saved to localStorage');
                     }
 
                     // 사용자 정보 저장
@@ -320,13 +324,16 @@
 
                     // 로그인 성공 메시지 표시
                     alertDiv.className = 'alert alert-success show';
-                    alertDiv.textContent = '로그인 성공! 대시보드로 이동합니다.';
+                    alertDiv.textContent = '로그인 성공! 대시보드로 이동합니다. (Blazor 초기화 중...)';
 
-                    // 쿠키가 설정되었으므로 짧은 대기 시간만 필요
-                    // (Blazor가 쿠키를 자동으로 인식함)
+                    // Blazor 앱이 로드되고 localStorage에서 토큰을 읽을 시간을 충분히 제공
+                    // 3초 대기 후 대시보드로 이동
+                    console.log('[Login] Waiting 3 seconds for Blazor to initialize...');
                     setTimeout(() => {
+                        console.log('[Login] Redirecting to dashboard');
+                        console.log('[Login] Token in localStorage:', localStorage.getItem('quant_admin_access_token') ? 'YES' : 'NO');
                         window.location.href = '/dashboard';
-                    }, 1000);
+                    }, 3000);
                 } else {
                     const data = await response.json();
                     alertDiv.className = 'alert alert-error show';