Add alpha session gate with cookie auth and login UI.

src/HSchool.AppHost/AppHost.cs

@@ -16,6 +16,7 @@ if (headless)
     server
         .WithEnvironment("Simulation__SavesDirectory", saves)
         .WithEnvironment("HSchool__AllowSaveReload", "true")
+        .WithEnvironment("HSchool__AlphaPassword", "test-alpha")
         .WithEnvironment("SwarmUi__BaseUrl", "");
 }