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/LoginPage.razor

@@ -0,0 +1,72 @@
+@page "/login"
+@inject IAccountManagement Acct
+@inject NavigationManager navigator
+
+<main class="PrimaryTheme">
+	<h1>Login</h1>
+
+	<section class="LoginForm">
+		<AuthorizeView>
+			<Authorized>
+				<div>You're logged in as @context.User.Identity?.Name.</div>
+			</Authorized>
+			<NotAuthorized>
+				@if (errorList.Length > 0)
+				{
+					<ul class="Errors" style="grid-area: errors">
+						@foreach (var error in errorList)
+						{
+							<li>@error</li>
+						}
+					</ul>
+				}
+
+				<label for="email" style="grid-area: emailLabel">Email</label>
+				<input required id="email" name="emailInput" type="email" style="grid-area: emailControl" @bind-value="email" />
+
+				<label for="password" style="grid-area: passLabel">Password</label>
+				<input required id="password" name="passwordInput" type="password" style="grid-area: passControl" @bind-value="password" />
+
+				<button style="grid-area: button" @onclick="DoLoginAsync">Login</button>
+			</NotAuthorized>
+		</AuthorizeView>
+	</section>
+
+</main>
+
+@code {
+	private string email = string.Empty;
+	private string password = string.Empty;
+	private string[] errorList = [];
+
+	public async Task DoLoginAsync()
+	{
+		errorList = [];
+
+		if (string.IsNullOrWhiteSpace(email))
+		{
+			errorList = ["Email is required."];
+
+			return;
+		}
+
+		if (string.IsNullOrWhiteSpace(password))
+		{
+			errorList = ["Password is required."];
+
+			return;
+		}
+
+		var result = await Acct.LoginAsync(email, password);
+
+		if (result.Succeeded)
+		{
+			email = password = string.Empty;
+			navigator.NavigateTo("/");
+		}
+		else
+		{
+			errorList = result.ErrorList;
+		}
+	}
+}