fix: wire up cancel reconnect button

[MojtabaMoslemyazdi]

Summary

The reconnect screen includes a "Cancel" button, but no click handler is registered for it. As a result, clicking the button has no effect.
This change registers the existing UI.cancelReconnect handler for the noVNC_cancel_reconnect_button element, making the button functional.

Changes

• Add click event listener for noVNC_cancel_reconnect_button
• Invoke the existing UI.cancelReconnect handler when the button is clicked

Testing

1. Enable automatic reconnect.
2. Disconnect the VNC session to trigger the reconnect screen.
3. Click the Cancel button.
4. Verify that the reconnect process is cancelled as expected.