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.

flake.nix

@@ -0,0 +1,121 @@
+{
+  description = "Home Lab NixOS Configuration - congenital-optimist & sleeper-service";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-25.05";
+    nixpkgs-unstable.url = "github:NixOS/nixpkgs/nixos-unstable";
+  };
+
+  outputs = { self, nixpkgs, nixpkgs-unstable, ... }@inputs: 
+  let
+    system = "x86_64-linux";
+    
+    # Create unstable package set
+    unstable = import nixpkgs-unstable {
+      inherit system;
+      config.allowUnfree = true;
+    };
+
+    # Shared special arguments for all machines
+    specialArgs = {
+      inherit inputs unstable;
+    };
+
+  in {
+    # NixOS system configurations
+    nixosConfigurations = {
+      
+      # congenital-optimist - AMD Threadripper workstation
+      congenital-optimist = nixpkgs.lib.nixosSystem {
+        inherit system specialArgs;
+        modules = [
+          ./machines/congenital-optimist/configuration.nix
+          ./machines/congenital-optimist/hardware-configuration.nix
+          ./modules/common/nix.nix
+          ./modules/common/base.nix
+          ./modules/common/tty.nix
+        ];
+      };
+
+      # sleeper-service - Intel Xeon file server
+      sleeper-service = nixpkgs.lib.nixosSystem {
+        inherit system specialArgs;
+        modules = [
+          ./machines/sleeper-service/configuration.nix
+          ./machines/sleeper-service/hardware-configuration.nix
+          ./modules/common/nix.nix
+          ./modules/common/base.nix
+          ./modules/common/tty.nix
+        ];
+      };
+    };
+
+    # Custom packages for the home lab
+    packages.${system} = import ./packages { 
+      pkgs = nixpkgs.legacyPackages.${system}; 
+    };
+
+    # Development shells for different projects
+    devShells.${system} = {
+      default = nixpkgs.legacyPackages.${system}.mkShell {
+        buildInputs = with nixpkgs.legacyPackages.${system}; [
+          nixd
+          alejandra
+          git
+          emacs
+        ];
+        shellHook = ''
+          echo "Home-lab development environment"
+          echo "Available configurations:"
+          echo "  - congenital-optimist (Threadripper workstation)"
+          echo "  - sleeper-service (Xeon file server)"
+          echo ""
+          echo "Build with: nixos-rebuild build --flake .#<config>"
+          echo "Switch with: nixos-rebuild switch --flake .#<config>"
+        '';
+      };
+
+      # Dotfiles development shell
+      dotfiles = nixpkgs.legacyPackages.${system}.mkShell {
+        buildInputs = with nixpkgs.legacyPackages.${system}; [
+          emacs
+          pandoc
+          starship
+        ];
+        shellHook = ''
+          echo "Literate dotfiles development environment"
+          echo "Tangle dotfiles with: emacs --batch -l org --eval \"(org-babel-tangle-file \\\"README.org\\\")\""
+        '';
+      };
+    };
+
+    # Overlays for package customizations
+    overlays.default = import ./overlays;
+
+    # Applications that can be run directly
+    apps.${system} = {
+      # Tangle all user dotfiles
+      tangle-dotfiles = {
+        type = "app";
+        program = "${nixpkgs.legacyPackages.${system}.writeShellScript "tangle-dotfiles" ''
+          cd users/geir/dotfiles
+          ${nixpkgs.legacyPackages.${system}.emacs}/bin/emacs --batch -l org --eval "(org-babel-tangle-file \"README.org\")"
+          echo "Dotfiles tangled successfully!"
+        ''}";
+      };
+
+      # Check flake configuration
+      check-config = {
+        type = "app";
+        program = "${nixpkgs.legacyPackages.${system}.writeShellScript "check-config" ''
+          echo "Checking flake configuration..."
+          nix flake check
+          echo "Configuration check complete!"
+        ''}";
+      };
+    };
+
+    # Formatter for Nix files
+    formatter.${system} = nixpkgs.legacyPackages.${system}.alejandra;
+  };
+}