Sets the wifi adapter into monitor mode, then listens to surrounding packets listing all detected devices into `wifi_map.yaml`.
Then, periodically filters the results by the mac addresses that opted in on the website from `identities.json` and sends all matched identities to the website via a signed webhook. This website stores the presence information locally and displays it with `website/index.php` with a timestamp of the last update.
Shows the last update of the `uploader.py` routine. It also allows to add identities by their name and mac and to delete identities by their mac. The mac addresses are hashed server-side and then stored into the world-accessible `identities.json`.
Put `scanner` onto the scanning device (e.g. Raspberry Pi). Let `scanner.sh` and `uploader.pu` running in the background, e.g. by the Systemd services below.