Standalone script that drops and re-establishes the router's PPPoE session
without a full reboot. Mirrors router_ui.py's RouterSession pattern: a
context manager that always logs out on exit, the CSRFToken header required
for writes since ABSB.5, and tolerant handling of the Disconnect/Connect
calls timing out with a Connect retry if the link doesn't come back up.
Confirmed working live: WAN IP and public IP (checked via api.ipify.org)
both changed after a run.
