Move Nix files into a nix directory

Move everything from `config` to the root level.

home/opdavies/default.nix

@@ -1,91 +0,0 @@
-{
-  config,
-  desktop,
-  inputs,
-  pkgs,
-  self,
-  username,
-  ...
-}:
-let
-  inherit (pkgs) lib;
-
-  desktop-config = import ./desktop.nix {
-    inherit
-      config
-      inputs
-      pkgs
-      username
-      ;
-  };
-  shared-config = import "${self}/lib/shared/home-manager.nix" {
-    inherit
-      inputs
-      pkgs
-      self
-      username
-      ;
-  };
-  shared-packages = import "${self}/lib/shared/home-manager-packages.nix" {
-    inherit
-      desktop
-      inputs
-      pkgs
-      username
-      ;
-  };
-in
-{
-  imports =
-    if desktop then
-      [
-        desktop-config
-        shared-config
-      ]
-    else
-      [ shared-config ];
-
-  home.packages =
-    shared-packages
-    ++ pkgs.lib.optionals desktop (
-      with pkgs;
-      [
-        brave
-        discord
-        gimp
-        gscan2pdf
-        handbrake
-        kdenlive
-        meslo-lg
-        obs-studio
-        okular
-        pamixer
-        pass
-        pavucontrol
-        pinentry
-        via
-        pocket-casts
-        xcape
-        xsel
-
-        pkgs.nixpkgs-2405.zoom-us
-      ]
-    );
-
-  home.sessionVariables = {
-    DIRENV_LOG_FORMAT = "";
-    EDITOR = "nvim";
-    LANG = "en_GB.UTF-8";
-    LC_ALL = "en_GB.UTF-8";
-    LC_CTYPE = "en_GB.UTF-8";
-    PATH = lib.concatStringsSep ":" [
-      "$PATH"
-      "$HOME/go/bin"
-      "./vendor/bin"
-      "./node_modules/.bin"
-    ];
-    PULUMI_SKIP_UPDATE_CHECK = "true";
-    REPOS = "$HOME/Code";
-    RIPGREP_CONFIG_PATH = "$HOME/.config/ripgrep/config";
-  };
-}

home/opdavies/desktop.nix

@@ -1,18 +0,0 @@
-{
-  config,
-  inputs,
-  pkgs,
-  username,
-}:
-{
-  imports = [
-    ../../modules/home-manager/alacritty.nix
-    ../../modules/home-manager/copyq.nix
-    ../../modules/home-manager/bluetuith.nix
-    ../../modules/home-manager/espanso.nix
-    ../../modules/home-manager/gtk.nix
-    ../../modules/home-manager/flameshot.nix
-    ../../modules/home-manager/gtk.nix
-    ../../modules/home-manager/mpv.nix
-  ];
-}