feat(nixos): consolidate hosts into a shared flake

Manage T450s, X1EG2 and Framework 13 from pinned NixOS inputs while retaining
machine-specific storage and hardware configuration.

Changes:

Shared Configuration:
- Extract common, KDE, desktop, development and Steam modules
- Share Emacs, VS Code, htop, DevOps tools and Docker across hosts
- Remove obsolete apps and global project language runtimes

Framework:
- Import the 11th-generation Intel hardware profile
- Enable Steam and ZFS with tookland/home mounted at /home
- Document manual ext4 root and ZFS installation steps
- Require installer-generated hardware configuration before installation

Validation:
- Evaluate both ThinkPads and Framework with test hardware
- Check Nix syntax, formatting and whitespace

modules/common.nix

@@ -0,0 +1,43 @@
+{ pkgs, ... }:
+{
+  nix.settings.experimental-features = [
+    "nix-command"
+    "flakes"
+  ];
+  nix.settings.auto-optimise-store = true;
+  nix.gc = {
+    automatic = true;
+    dates = "weekly";
+    options = "--delete-older-than 30d";
+  };
+  nixpkgs.config.allowUnfree = true;
+
+  networking.networkmanager.enable = true;
+  time.timeZone = "Africa/Tunis";
+  i18n.defaultLocale = "en_US.UTF-8";
+  i18n.extraLocaleSettings = {
+    LC_ADDRESS = "en_US.UTF-8";
+    LC_IDENTIFICATION = "en_US.UTF-8";
+    LC_MEASUREMENT = "en_US.UTF-8";
+    LC_MONETARY = "en_US.UTF-8";
+    LC_NAME = "en_US.UTF-8";
+    LC_NUMERIC = "en_US.UTF-8";
+    LC_PAPER = "en_US.UTF-8";
+    LC_TELEPHONE = "en_US.UTF-8";
+    LC_TIME = "en_US.UTF-8";
+  };
+
+  users.users.clw = {
+    isNormalUser = true;
+    description = "Chris Wong";
+    shell = pkgs.zsh;
+    extraGroups = [
+      "networkmanager"
+      "wheel"
+      "scanner"
+      "lp"
+    ];
+    packages = [ pkgs.firefox ];
+  };
+  programs.zsh.enable = true;
+}

modules/desktop-apps.nix

@@ -0,0 +1,19 @@
+{ pkgs, ... }:
+{
+  # Shared desktop applications; imported by the two ThinkPads.
+  environment.systemPackages = with pkgs; [
+    bitwarden-desktop
+    brave
+    flatpak
+    google-chrome
+    jellyfin-desktop
+    libreoffice-qt
+    mpv
+    remmina
+    rocketchat-desktop
+    signal-desktop
+    tailscale
+    virt-manager
+    vlc
+  ];
+}

modules/development.nix

@@ -0,0 +1,48 @@
+{ pkgs, ... }:
+{
+  # Workstation tools only; language runtimes and SDKs belong in projects.
+  environment.systemPackages = with pkgs; [
+    # Editors and shell utilities.
+    emacs
+    vscode
+    git
+    htop
+    tmux
+    ripgrep
+    fd
+    duf
+    dust
+    killall
+    lsof
+    rsync
+    unzip
+    zip
+
+    # Infrastructure, containers, and structured data.
+    ansible
+    awscli2
+    docker-compose
+    jq
+    yq-go
+
+    # Networking and security tools.
+    openssh
+    gnupg
+    openssl
+    curl
+    dig
+    mosh
+    tcpdump
+    wget
+    whois
+    wireguard-tools
+  ];
+
+  virtualisation.docker.enable = true;
+  users.users.clw.extraGroups = [ "docker" ];
+
+  programs.direnv = {
+    enable = true;
+    nix-direnv.enable = true;
+  };
+}

modules/gaming.nix

@@ -0,0 +1,9 @@
+{ ... }:
+{
+  # Import on machines where Steam is wanted.
+  programs.steam = {
+    enable = true;
+    remotePlay.openFirewall = true;
+    dedicatedServer.openFirewall = true;
+  };
+}

modules/kde.nix

@@ -0,0 +1,23 @@
+{ ... }:
+{
+  services.xserver.enable = true;
+  services.xserver.xkb = {
+    layout = "us";
+    variant = "";
+  };
+  services.displayManager.sddm.enable = true;
+  services.desktopManager.plasma6.enable = true;
+  programs.dconf.enable = true;
+  services.printing.enable = true;
+  services.flatpak.enable = true;
+  hardware.bluetooth.enable = true;
+
+  security.rtkit.enable = true;
+  services.pipewire = {
+    enable = true;
+    alsa.enable = true;
+    alsa.support32Bit = true;
+    pulse.enable = true;
+    jack.enable = true;
+  };
+}