Add ntfy role

UnifiedPush is provided via ntfy on push.darmstadt.social. A role has to be added though and some features / configuration is still missing:

• deploy app
• add role
• fail2ban with traefik(?) https://docs.ntfy.sh/config/#banning-bad-actors-fail2ban | https://stackoverflow.com/questions/52123355/how-to-implement-fail2ban-with-traefik
• rate-limiting https://docs.ntfy.sh/config/#rate-limiting
• ability to configure private-server mode https://docs.ntfy.sh/config/#example-unifiedpush
• monitoring https://docs.ntfy.sh/config/#monitoring