extra-container uses a minimal NixOS module set for fast evaluation.
nixpkgs unstable added nixos-init.nix and systemd.nix now references
config.system.nixos-init.package, but extra-container's module set
doesn't include it.

Add a dummy nixos-init.package option to the outer container config,
matching extra-container's existing pattern for missing options.

Also fixes services.mingetty -> services.getty rename in virtulus.

The pixel8 Linux project has been extracted into its own repository.
This also fixes the nix flake check failure (pixel8 was missing
nixpkgs.hostPlatform).

- Radicale with htpasswd auth (bcrypt), proxied via nginx with ACME
- DNS CNAME for cal.lassul.us -> neoprism
- Auto-generated password stored in clan vars
- User: opencrow
- Compatible with DAVx5 (Android), Thunderbird, etc.

FlakeHub authentication is failing, causing CI to error out.
Disable it since we only need the local nix cache.

Set OPENCROW_HEARTBEAT_INTERVAL=10m. Bot uses nix run nixpkgs#notmuch
for mail indexing — no extra packages needed in the config.