startAutoClearTimer method
Starts an auto-clear timer that will call onTimeout after timeout
duration of inactivity.
The timer resets whenever resetTimer is called (typically when user
interacts with the PIN input).
Implementation
void startAutoClearTimer({
required Duration timeout,
required VoidCallback onTimeout,
}) {
_autoClearTimer?.cancel();
_autoClearTimer = Timer(timeout, onTimeout);
}