Add a zfs-alerts module that runs a daily health check on ZFS machines,
sending detailed ntfy notifications for degraded pools, data errors, or
drive errors. Introduce an "ntfy" system role to decouple ntfy alerting
from the server/personal roles, and assign it to all machines.
Highlights
- No need to update flake for every machine anymore, just add a properties.nix file.
- Roles are automatically generated from all machine configurations.
- Roles and their secrets automatically are grouped and show up in agenix secrets.nix
- Machines and their service configs may now query the properties of all machines.
- Machine configuration and secrets are now competely isolated into each machine's directory.
- Safety checks to ensure no mixing of luks unlocking secrets and hosts with primary ones.
- SSH pubkeys no longer centrally stored but instead per machine where the private key lies for better cleanup.
