feat: add dotfiles submodule and home-manager config

- Add dotfiles repo as submodule in assets/dotfiles/
- Rewrite home.nix with direct file references instead of stow service
- Remove old custom dotfiles.nix service (replaced by home-manager)
- Clean up services/default.nix import

modules/nixos/services/default.nix

@@ -1,6 +1,5 @@
 {
   imports = [
-    ./dotfiles.nix
     ./systemd
   ];
 }

modules/nixos/services/dotfiles.nix

@@ -1,69 +0,0 @@
-{ config, lib, pkgs, ... }:
-
-with lib;
-
-let
-  cfg = config.services.dotfiles;
-  stowDir = cfg.stowDir;
-
-  # Function to recursively find all files in a directory
-  findFiles = dir:
-    let
-      files = builtins.attrNames (builtins.readDir dir);
-    in
-      concatMap (name:
-        let
-          path = dir + "/${name}";
-        in
-          if (builtins.typeOf (builtins.readDir path) == "set")
-          then findFiles path
-          else [ path ]
-      ) files;
-
-  # Get a list of all packages (directories) in the stow directory
-  stowPackages = builtins.attrNames (builtins.readDir stowDir);
-
-  # Create an attribute set where each attribute is a package name
-  # and the value is a list of files to be linked.
-  homeManagerLinks = listToAttrs (map (pkg:
-    let
-      pkgPath = stowDir + "/${pkg}";
-      files = findFiles pkgPath;
-    in
-      nameValuePair pkg (map (file: {
-        source = file;
-        target = removePrefix (pkgPath + "/") file;
-      }) files)
-  ) stowPackages);
-
-in
-{
-  options.services.dotfiles = {
-    enable = mkEnableOption "Enable dotfiles management";
-
-    stowDir = mkOption {
-      type = types.path;
-      description = "The directory where your stow packages are located.";
-    };
-
-    user = mkOption {
-      type = types.str;
-      description = "The user to manage dotfiles for.";
-    };
-  };
-
-  config = mkIf cfg.enable {
-    home-manager.users.${cfg.user} = {
-      home.file =
-        let
-          allFiles = concatLists (attrValues homeManagerLinks);
-        in
-          listToAttrs (map (file:
-            nameValuePair file.target {
-              source = file.source;
-            }
-          ) allFiles);
-    };
-  };
-}
-