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.Api/Controllers/AccountController.cs

@@ -0,0 +1,74 @@
+using Microsoft.AspNetCore.Authorization;
+using Microsoft.AspNetCore.Identity;
+using Microsoft.AspNetCore.Mvc;
+using Shogi.Api.Identity;
+using System.Security.Claims;
+
+namespace Shogi.Api.Controllers;
+
+[Authorize]
+[Route("[controller]")]
+[ApiController]
+public class AccountController(
+	SignInManager<ShogiUser> signInManager,
+	UserManager<ShogiUser> UserManager,
+	IConfiguration configuration) : ControllerBase
+{
+	[Authorize("Admin")]
+	[HttpPost("TestAccount")]
+	public async Task<IActionResult> CreateTestAccounts()
+	{
+		var newUser = new ShogiUser { UserName = "aat-account", Email = "test-account@lucaserver.space", EmailConfirmed = true };
+		var newUser2 = new ShogiUser { UserName = "aat-account-2", Email = "test-account2@lucaserver.space", EmailConfirmed = true };
+		var pass = configuration["TestUserPassword"] ?? throw new InvalidOperationException("TestUserPassword not configured.");
+		var result = await UserManager.CreateAsync(newUser, pass);
+		if (result != null && !result.Succeeded)
+		{
+			return this.Problem(string.Join(",", result.Errors.Select(e => e.Description)));
+		}
+
+		result = await UserManager.CreateAsync(newUser2, pass);
+		if(result != null && !result.Succeeded)
+		{
+			return this.Problem(string.Join(",", result.Errors.Select(e => e.Description)));
+		}
+
+		return this.Created();
+	}
+
+	[HttpPost("/logout")]
+	public async Task<IActionResult> Logout([FromBody] object empty)
+	{
+		// https://learn.microsoft.com/aspnet/core/blazor/security/webassembly/standalone-with-identity#antiforgery-support
+		if (empty is not null)
+		{
+			await signInManager.SignOutAsync();
+
+			return this.Ok();
+		}
+
+		return this.Unauthorized();
+	}
+
+	[HttpGet("/roles")]
+	public IActionResult GetRoles()
+	{
+		if (this.User.Identity is not null && this.User.Identity.IsAuthenticated)
+		{
+			var identity = (ClaimsIdentity)this.User.Identity;
+			var roles = identity.FindAll(identity.RoleClaimType)
+					.Select(c => new
+					{
+						c.Issuer,
+						c.OriginalIssuer,
+						c.Type,
+						c.Value,
+						c.ValueType
+					});
+
+			return this.Ok(roles);
+		}
+
+		return this.Unauthorized();
+	}
+}