I have seen in other captive portals where the word "logout" is typed in browser address bar.
This is much simpler solution, but how to implement it?
It needs some intercept/analysis of http request for word "logout" and then redirect to the logout URL.
Maybe this could be put in captive portal code or squid proxy config or where?
Also, would be useful to type "status" into address bar and get page back showing time remaining, etc.