modules: add homelab.host for host metadata

Add a shared `homelab.host` module that provides host metadata for
multiple consumers:
- tier: deployment tier (test/prod) for future homelab-deploy service
- priority: alerting priority (high/low) for Prometheus label filtering
- role: primary role of the host (dns, database, monitoring, etc.)
- labels: free-form labels for additional metadata

Host configurations updated with appropriate values:
- ns1, ns2: role=dns with dns_role labels
- nix-cache01: priority=low, role=build-host
- vault01: role=vault
- jump: role=bastion
- template, template2, testvm01, vaulttest01: tier=test, priority=low

The module is now imported via commonModules in flake.nix, making it
available to all hosts including minimal configurations like template2.

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

hosts/jump/configuration.nix

@@ -8,6 +8,9 @@
     ];
 
   nixpkgs.config.allowUnfree = true;
+
+  homelab.host.role = "bastion";
+
   # Use the systemd-boot EFI boot loader.
   boot.loader.grub.enable = true;
   boot.loader.grub.device = "/dev/sda";

hosts/nix-cache01/configuration.nix

@@ -13,6 +13,11 @@
 
   homelab.dns.cnames = [ "nix-cache" "actions1" ];
 
+  homelab.host = {
+    priority = "low";
+    role = "build-host";
+  };
+
   fileSystems."/nix" = {
     device = "/dev/disk/by-label/nixcache";
     fsType = "xfs";

hosts/ns1/configuration.nix

@@ -49,6 +49,11 @@
   ];
   vault.enable = true;
 
+  homelab.host = {
+    role = "dns";
+    labels.dns_role = "primary";
+  };
+
   nix.settings.tarball-ttl = 0;
   environment.systemPackages = with pkgs; [
     vim

hosts/ns2/configuration.nix

@@ -49,6 +49,11 @@
   ];
   vault.enable = true;
 
+  homelab.host = {
+    role = "dns";
+    labels.dns_role = "secondary";
+  };
+
   environment.systemPackages = with pkgs; [
     vim
     wget

hosts/template/configuration.nix

@@ -11,6 +11,11 @@
   # Template host - exclude from DNS zone generation
   homelab.dns.enable = false;
 
+  homelab.host = {
+    tier = "test";
+    priority = "low";
+  };
+
 
   boot.loader.grub.enable = true;
   boot.loader.grub.device = "/dev/sda";

hosts/template2/configuration.nix

@@ -32,6 +32,11 @@
     datasource_list = [ "ConfigDrive" "NoCloud" ];
   };
 
+  homelab.host = {
+    tier = "test";
+    priority = "low";
+  };
+
   boot.loader.grub.enable = true;
   boot.loader.grub.device = "/dev/vda";
   networking.hostName = "nixos-template2";

hosts/testvm01/configuration.nix

@@ -16,6 +16,11 @@
   # Test VM - exclude from DNS zone generation
   homelab.dns.enable = false;
 
+  homelab.host = {
+    tier = "test";
+    priority = "low";
+  };
+
   nixpkgs.config.allowUnfree = true;
   boot.loader.grub.enable = true;
   boot.loader.grub.device = "/dev/vda";

hosts/vault01/configuration.nix

@@ -16,6 +16,8 @@
 
   homelab.dns.cnames = [ "vault" ];
 
+  homelab.host.role = "vault";
+
   nixpkgs.config.allowUnfree = true;
   boot.loader.grub.enable = true;
   boot.loader.grub.device = "/dev/vda";

hosts/vaulttest01/configuration.nix

@@ -39,6 +39,12 @@ in
     ../../common/vm
   ];
 
+  homelab.host = {
+    tier = "test";
+    priority = "low";
+    role = "vault";
+  };
+
   nixpkgs.config.allowUnfree = true;
   boot.loader.grub.enable = true;
   boot.loader.grub.device = "/dev/vda";