Fix public home routing and add home smoke test

src/TaxBaik.Web.Client/Components/Admin/RedirectToLogin.razor

@@ -6,7 +6,31 @@
         if (!firstRender)
             return;
 
-        var returnUrl = Uri.EscapeDataString(Navigation.ToBaseRelativePath(Navigation.Uri));
+        var returnUrl = Uri.EscapeDataString(GetSafeReturnUrl());
         Navigation.NavigateTo($"/taxbaik/admin/login?returnUrl={returnUrl}", replace: true);
     }
+
+    private string GetSafeReturnUrl()
+    {
+        try
+        {
+            var current = new Uri(Navigation.Uri);
+            var baseUri = new Uri(Navigation.BaseUri);
+
+            if (current.IsAbsoluteUri &&
+                string.Equals(current.Scheme, baseUri.Scheme, StringComparison.OrdinalIgnoreCase) &&
+                string.Equals(current.Authority, baseUri.Authority, StringComparison.OrdinalIgnoreCase) &&
+                current.AbsolutePath.StartsWith(baseUri.AbsolutePath, StringComparison.OrdinalIgnoreCase))
+            {
+                var relative = current.AbsolutePath[baseUri.AbsolutePath.Length..] + current.Query + current.Fragment;
+                return string.IsNullOrWhiteSpace(relative) ? "dashboard" : relative.TrimStart('/');
+            }
+        }
+        catch
+        {
+            // Fall through to a safe default.
+        }
+
+        return "dashboard";
+    }
 }

src/TaxBaik.Web/Program.cs

@@ -476,8 +476,9 @@ app.MapHealthChecks("/healthz");
 app.MapRazorPages();  // Sitemap.cshtml, Rss.cshtml, Feed.cshtml
 app.MapStaticAssets();
 
-// Blazor WebAssembly - prerender 지원
-app.MapRazorComponents<TaxBaik.WasmClient.Components.Admin.App>()
+// Blazor WebAssembly - 관리자 앱은 /taxbaik/admin 아래에서만 렌더링
+app.MapGroup("/taxbaik/admin")
+   .MapRazorComponents<TaxBaik.WasmClient.Components.Admin.App>()
    .AddInteractiveWebAssemblyRenderMode()
    .AllowAnonymous();