WBS-11: Hardening BFF Architecture, fix /Index page redirect and JsonDocument ObjectDisposedException in operational-report API

src/dotnet/QuantEngine.Web/Pages/Account/Login.cshtml

@@ -223,6 +223,7 @@
         }
 
         <form method="post" class="login-form">
+            @Html.AntiForgeryToken()
             <div class="form-group">
                 <label for="username" class="form-label">관리자 아이디</label>
                 <input

src/dotnet/QuantEngine.Web/Pages/Account/Login.cshtml.cs

@@ -42,7 +42,8 @@ namespace QuantEngine.Web.Pages.Account
             try
             {
                 var loginRequest = new { Username = username, Password = password };
-                var response = await _httpClient.PostAsJsonAsync("/api/auth/login", loginRequest);
+                var requestUri = $"{Request.Scheme}://{Request.Host}/api/auth/login";
+                var response = await _httpClient.PostAsJsonAsync(requestUri, loginRequest);
 
                 if (response.IsSuccessStatusCode)
                 {
@@ -64,7 +65,7 @@ namespace QuantEngine.Web.Pages.Account
                         Response.Cookies.Delete("quant_admin_username");
                     }
 
-                    return RedirectToPage("/Index");
+                    return Redirect("/");
                 }
                 else
                 {