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/Identity/FormResult.cs

@@ -0,0 +1,14 @@
+namespace Shogi.UI.Identity;
+
+public class FormResult
+{
+	/// <summary>
+	/// Gets or sets a value indicating whether the action was successful.
+	/// </summary>
+	public bool Succeeded { get; set; }
+
+	/// <summary>
+	/// On failure, the problem details are parsed and returned in this array.
+	/// </summary>
+	public string[] ErrorList { get; set; } = [];
+}