add gateway for admeme (#17587)

Co-authored-by: deltanedas <@deltanedas:kde.org>

Content.Client/Gateway/UI/GatewayBoundUserInterface.cs

@@ -0,0 +1,43 @@
+using Content.Shared.Gateway;
+using Robust.Client.GameObjects;
+
+namespace Content.Client.Gateway.UI;
+
+public sealed class GatewayBoundUserInterface : BoundUserInterface
+{
+    private GatewayWindow? _window;
+
+    public GatewayBoundUserInterface(ClientUserInterfaceComponent owner, Enum uiKey) : base(owner, uiKey)
+    {
+    }
+
+    protected override void Open()
+    {
+        base.Open();
+
+        _window = new GatewayWindow();
+        _window.OpenPortal += destination =>
+        {
+            SendMessage(new GatewayOpenPortalMessage(destination));
+        };
+        _window.OnClose += Close;
+        _window?.OpenCentered();
+    }
+
+    protected override void Dispose(bool disposing)
+    {
+        base.Dispose(disposing);
+        _window?.Dispose();
+        _window = null;
+    }
+
+    protected override void UpdateState(BoundUserInterfaceState state)
+    {
+        base.UpdateState(state);
+
+        if (state is not GatewayBoundUserInterfaceState current)
+            return;
+
+        _window?.UpdateState(current);
+    }
+}