Replace custom socket implementation with SignalR.

Replace MSAL and custom cookie auth with Microsoft.Identity.EntityFramework
Also some UI redesign to accommodate different login experience.

Shogi.UI/Pages/Identity/LogoutPage.razor

@@ -0,0 +1,30 @@
+@page "/logout"
+@inject IAccountManagement Acct
+
+<main class="PrimaryTheme">
+	<h1>Logout</h1>
+
+	<AuthorizeView @ref="authView">
+		<Authorized>
+			<div class="alert alert-info">Logging you out...</div>
+		</Authorized>
+		<NotAuthorized>
+			<p>Thanks for playing!</p>
+			<div class="alert alert-success">You're logged out. <a href="/login">Log in.</a></div>
+		</NotAuthorized>
+	</AuthorizeView>
+</main>
+
+@code {
+	private AuthorizeView? authView;
+
+	protected override async Task OnInitializedAsync()
+	{
+		if (await Acct.CheckAuthenticatedAsync())
+		{
+			await Acct.LogoutAsync();
+		}
+
+		await base.OnInitializedAsync();
+	}
+}