add aspects/desktop/ modules

Desktop-specific NixOS and home-manager configuration:
boot, desktop, niri, nix, services

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

aspects/desktop/services.nix

@@ -0,0 +1,19 @@
+{ inputs, ... }:
+{
+  flake.modules.nixos.desktop-services = { config, lib, pkgs, ... }: {
+    # Import parent aspect for inheritance
+    imports = [ inputs.self.modules.nixos.common-services ];
+
+    services = {
+      printing.enable = true;
+      udev.packages = with pkgs; [ yubikey-personalization ];
+      keyd = {
+        enable = true;
+        keyboards.all = {
+          ids = [ "*" ];
+          settings.main.capslock = "overload(meta, esc)";
+        };
+      };
+    };
+  };
+}