foulab/foudoor: foudoor: open the lab door by logging in via SSH - Codeberg.org

* door.sh: update for gpio interface in 6.12 kernel
* door.sh: rewrite to retain trap so it boots you at the end of the timeout, instead of end of session
* door.sh: use hold-period, remove trap
The previous approach introduced a situation where the door could
get stuck open or un-openable due to a dangling gpioset process
holding the door open.
Setting an explicit hold period avoids this issue, and in initial
tests exiting early, seems to clean up as expected.