feat: add Home Manager refactoring plan and initial structure

- Add comprehensive Home Manager refactoring plan document
- Create initial Home Manager directory structure with user configs
- Add modular Emacs configuration for Home Manager integration
- Update system configurations for Home Manager compatibility
- Preserve existing functionality while preparing for migration

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

modules/desktop/niri.nix

@@ -4,7 +4,10 @@
   pkgs,
   ...
 }: {
-  programs.niri.enable = true;
+  programs.niri = {
+    enable = true;
+  };
+
   environment.systemPackages = with pkgs; [
     # Niri scrolling window manager
     niri

modules/desktop/waybar.nix

@@ -13,7 +13,7 @@
         "position": "top",
         "height": 30,
         "spacing": 4,
-        "modules-left": ["sway/workspaces"],
+        "modules-left": ["niri/workspaces"],
         "modules-center": [],
         "modules-right": ["network", "clock"],
         "sway/workspaces": {

modules/development/emacs.nix

@@ -87,6 +87,7 @@ with lib; let
         doom-themes
         doom-modeline
         all-the-icons
+        all-the-icons-completion
         rainbow-delimiters
         highlight-indent-guides