refactor(wbs-ux): route root authenticated users to Vue templates and map SPA fallback

src/dotnet/QuantEngine.Web/Pages/Admin/_AdminLayout.cshtml

@@ -50,7 +50,9 @@
                 <li class="nav-item"><a class="nav-link text-white py-1 px-3 @NavActive("/Admin/Database")" href="/Admin/Database">DB 테이블 관리</a></li>
                 <li class="nav-item"><a class="nav-link text-white py-1 px-3 @NavActive("/Admin/Users")" href="/Admin/Users">사용자 관리</a></li>
                 <li class="nav-item"><a class="nav-link text-white py-1 px-3 @NavActive("/Admin/Operations")" href="/Admin/Operations">운영 관리</a></li>
+                <li class="nav-item"><a class="nav-link py-1 px-3 font-weight-bold" style="color: #F1C40F;" href="/templates">🛠️ 프로토타입 갤러리</a></li>
             </ul>
+
         </div>
 
         <!-- 2. Center High-Density Data Grid Body -->

src/dotnet/QuantEngine.Web/Program.cs

@@ -192,11 +192,11 @@ try
         Log.Warning("Hangfire setup failed: {Message}", ex.Message);
     }
 
-    // Root redirect: unauthenticated → /Account/Login, authenticated → /Admin/Dashboard
+    // Root redirect: unauthenticated → /Account/Login, authenticated → Vue 3 SPA /templates
     app.MapGet("/", context =>
     {
         if (context.User?.Identity?.IsAuthenticated ?? false)
-            context.Response.Redirect("/Admin/Dashboard");
+            context.Response.Redirect("/templates");
         else
             context.Response.Redirect("/Account/Login");
         return Task.CompletedTask;
@@ -210,6 +210,8 @@ try
     });
 
     app.MapRazorPages();
+    app.MapFallbackToFile("index.html");
+
 
     app.Run();
 }