hosts: decommission ca host and remove labmon

Remove the step-ca host and labmon flake input now that ACME has been
migrated to OpenBao PKI.

Removed:
- hosts/ca/ - step-ca host configuration
- services/ca/ - step-ca service module
- labmon flake input and module (no longer used)

Updated:
- flake.nix - removed ca host and labmon references
- flake.lock - removed labmon input
- rebuild-all.sh - removed ca from host list
- CLAUDE.md - updated documentation

Note: secrets/ca/ should be manually removed by the user.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

hosts/ca/configuration.nix

@@ -1,63 +0,0 @@
-{
-  pkgs,
-  ...
-}:
-
-{
-  imports = [
-    ../template/hardware-configuration.nix
-
-    ../../system
-    ../../common/vm
-  ];
-
-  nixpkgs.config.allowUnfree = true;
-  # Use the systemd-boot EFI boot loader.
-  boot.loader.grub = {
-    enable = true;
-    device = "/dev/sda";
-    configurationLimit = 3;
-  };
-
-  networking.hostName = "ca";
-  networking.domain = "home.2rjus.net";
-  networking.useNetworkd = true;
-  networking.useDHCP = false;
-  services.resolved.enable = true;
-  networking.nameservers = [
-    "10.69.13.5"
-    "10.69.13.6"
-  ];
-
-  systemd.network.enable = true;
-  systemd.network.networks."ens18" = {
-    matchConfig.Name = "ens18";
-    address = [
-      "10.69.13.12/24"
-    ];
-    routes = [
-      { Gateway = "10.69.13.1"; }
-    ];
-    linkConfig.RequiredForOnline = "routable";
-  };
-  time.timeZone = "Europe/Oslo";
-
-  nix.settings.experimental-features = [
-    "nix-command"
-    "flakes"
-  ];
-  nix.settings.tarball-ttl = 0;
-  environment.systemPackages = with pkgs; [
-    vim
-    wget
-    git
-  ];
-
-  # Open ports in the firewall.
-  # networking.firewall.allowedTCPPorts = [ ... ];
-  # networking.firewall.allowedUDPPorts = [ ... ];
-  # Or disable the firewall altogether.
-  networking.firewall.enable = false;
-
-  system.stateVersion = "23.11"; # Did you read the comment?
-}

hosts/ca/default.nix

@@ -1,7 +0,0 @@
-{ ... }:
-{
-  imports = [
-    ./configuration.nix
-    ../../services/ca
-  ];
-}