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/Play/GameBoard/SeatedGameBoard.razor

@@ -0,0 +1,128 @@
+@using Shogi.Contracts.Api;
+@using Shogi.Contracts.Types;
+@using System.Text.RegularExpressions;
+@using System.Net;
+@inject PromotePrompt PromotePrompt;
+@inject ShogiApi ShogiApi;
+
+<GameBoardPresentation Session="Session"
+											 Perspective="Perspective"
+											 OnClickHand="OnClickHand"
+											 OnClickTile="OnClickTile"
+											 SelectedPosition="@selectedBoardPosition"
+											 SelectedPieceFromHand="@selectedPieceFromHand"
+											 IsMyTurn="IsMyTurn" />
+
+@code {
+	[Parameter, EditorRequired]
+	public WhichPlayer Perspective { get; set; }
+	[Parameter, EditorRequired]
+	public Session Session { get; set; } = default!;
+	private bool IsMyTurn => Session?.BoardState.WhoseTurn == Perspective;
+	private string? selectedBoardPosition;
+	private WhichPiece? selectedPieceFromHand;
+
+	protected override void OnParametersSet()
+	{
+		base.OnParametersSet();
+		selectedBoardPosition = null;
+		selectedPieceFromHand = null;
+		if (Session == null)
+		{
+			throw new ArgumentException($"{nameof(Session)} cannot be null.", nameof(Session));
+		}
+	}
+
+	bool ShouldPromptForPromotion(string position)
+	{
+		if (Perspective == WhichPlayer.Player1 && Regex.IsMatch(position, ".[7-9]"))
+		{
+			return true;
+		}
+		if (Perspective == WhichPlayer.Player2 && Regex.IsMatch(position, ".[1-3]"))
+		{
+			return true;
+		}
+		return false;
+	}
+
+	async Task OnClickTile(Piece? pieceAtPosition, string position)
+	{
+		if (!IsMyTurn) return;
+
+
+		if (selectedBoardPosition == position)
+		{
+			// Deselect the selected position.
+			selectedBoardPosition = null;
+			StateHasChanged();
+			return;
+		}
+
+		if (selectedBoardPosition == null && pieceAtPosition?.Owner == Perspective)
+		{
+			// Select an owned piece.
+			selectedBoardPosition = position;
+			// Prevent selecting pieces from the hand and board at the same time.
+			selectedPieceFromHand = null;
+			StateHasChanged();
+			return;
+		}
+
+		if (selectedPieceFromHand is not null)
+		{
+			if (pieceAtPosition is null)
+			{
+				// Placing a piece from the hand to an empty space.
+				var success = await ShogiApi.Move(
+						Session.SessionId.ToString(),
+						new MovePieceCommand(selectedPieceFromHand.Value, position));
+				if (!success)
+				{
+					selectedPieceFromHand = null;
+				}
+			}
+			StateHasChanged();
+			return;
+		}
+
+		if (selectedBoardPosition != null)
+		{
+			if (pieceAtPosition == null || pieceAtPosition?.Owner != Perspective)
+			{
+				// Moving to an empty space or capturing an opponent's piece.
+				if (ShouldPromptForPromotion(position) || ShouldPromptForPromotion(selectedBoardPosition))
+				{
+					PromotePrompt.Show(
+							Session.SessionId.ToString(),
+							new MovePieceCommand(selectedBoardPosition, position, false));
+				}
+				else
+				{
+					var success = await ShogiApi.Move(Session.SessionId.ToString(), new MovePieceCommand(selectedBoardPosition, position, false));
+					if (!success)
+					{
+						selectedBoardPosition = null;
+					}
+				}
+				StateHasChanged();
+				return;
+			}
+		}
+	}
+
+	async Task OnClickHand(Piece piece)
+	{
+		if (!IsMyTurn) return;
+
+		// Prevent selecting from both the hand and the board.
+		selectedBoardPosition = null;
+
+		selectedPieceFromHand = piece.WhichPiece == selectedPieceFromHand
+				// Deselecting the already-selected piece
+				? selectedPieceFromHand = null
+				: selectedPieceFromHand = piece.WhichPiece;
+
+		StateHasChanged();
+	}
+}