hosts: add role metadata to all hosts

Assign roles to hosts for better organization and filtering:
- ha1: home-automation
- monitoring01, monitoring02: monitoring
- jelly01: media
- nats1: messaging
- http-proxy: proxy
- testvm01-03: test

Also promote kanidm01 and monitoring02 from test to prod tier.

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

hosts/nats1/configuration.nix

@@ -11,6 +11,8 @@
     ../../common/vm
   ];
 
+  homelab.host.role = "messaging";
+
   nixpkgs.config.allowUnfree = true;
   # Use the systemd-boot EFI boot loader.
   boot.loader.grub = {