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/Identity/ShogiUser.cs

@@ -0,0 +1,7 @@
+using Microsoft.AspNetCore.Identity;
+
+namespace Shogi.Api.Identity;
+
+public class ShogiUser : IdentityUser
+{
+}