feat: initial NixOS home lab infrastructure setup

- Add modular flake-based NixOS configuration
- Implement GitOps foundation with CI/CD pipeline
- Create comprehensive documentation and branching strategy
- Add modular desktop environments (GNOME, Cosmic, Sway)
- Configure virtualization stack (Incus, Libvirt, Podman)
- Set up development tools and hardware-specific modules
- Establish user configuration with literate programming support

This commit represents the completion of Phase 1: Flakes Migration
with modular configuration, virtualization, and GitOps foundation.

modules/desktop/gnome.nix

@@ -0,0 +1,22 @@
+{ config, pkgs, ... }: {
+  # GNOME Desktop Environment
+  services.xserver = {
+    enable = true;
+    desktopManager.gnome.enable = true;
+    xkb.layout = "no";
+  };
+
+  # GNOME-specific packages
+  environment.systemPackages = with pkgs; [
+    gnome-extension-manager
+    gnome-shell-extensions
+    dconf-editor
+    gnome-tweaks
+  ];
+  
+  # GNOME services
+  services.gnome = {
+    gnome-keyring.enable = true;
+    glib-networking.enable = true;
+  };
+}