Implement milestone 2 route navigation

RpgRoller.Tests/Api/FrontendHostTests.cs

@@ -40,4 +40,20 @@ public sealed class FrontendHostTests(WebApplicationFactory<Program> factory) :
         Assert.Contains("data-auth-page", html);
         Assert.DoesNotContain("_framework/blazor.web.js", html);
     }
+
+    [Theory]
+    [InlineData("/play")]
+    [InlineData("/campaigns")]
+    [InlineData("/admin")]
+    public async Task AuthenticatedRoutes_ServeInteractiveShell(string path)
+    {
+        using var factory = CreateFactory(1);
+        using var client = factory.CreateClient(new() { AllowAutoRedirect = false });
+        var response = await client.GetAsync(path);
+
+        Assert.Equal(HttpStatusCode.OK, response.StatusCode);
+        var html = await response.Content.ReadAsStringAsync();
+        Assert.Contains("_framework/blazor.web.js", html);
+        Assert.DoesNotContain("data-auth-page", html);
+    }
 }