Add Niri desktop configuration with integrated utilities

- Introduced a new power menu script using fuzzel for session management.
- Updated Bellerophon configuration to include Niri desktop and its components.
- Removed obsolete README for Niri and consolidated its configuration files.
- Added swayidle and swaylock integration for idle management and screen locking.
- Implemented waybar for status bar functionality with basic configuration.
- Created fuzzel integration for application launching and menu access.
- Added zenbook debugging scripts for display and keyboard diagnostics.
- Migrated keyring and other configurations to streamline Niri setup.
- Enhanced display management with systemd services for better integration.

hosts/common/optional/niri.nix

@@ -5,10 +5,31 @@
 }: {
   imports = [
     inputs.niri.nixosModules.niri
+    (import ./niri/waybar.nix)
+    (import ./niri/swayidle.nix)
+    (import ./niri/fuzzel.nix)
+    (import ./niri/swaylock.nix)
   ];
 
   programs.niri.enable = true;
 
+  # Enable UWSM (Universal Wayland Session Manager) for better session management
+  # See docs/uwsm-niri-integration.md for usage and migration guide
+  programs.uwsm = {
+    enable = true;
+    waylandCompositors = {
+      niri = {
+        prettyName = "Niri";
+        comment = "Niri scrollable-tiling Wayland compositor managed by UWSM";
+        binPath = "/run/current-system/sw/bin/niri-session";
+      };
+    };
+  };
+
+  # UWSM provides better environment variable inheritance and systemd integration
+  # All startup applications are now managed via systemd.user.services with
+  # WantedBy=["graphical-session.target"] in the home-manager configuration
+
   # Use KDE portal instead of GNOME for better KDE integration
   xdg.portal = {
     enable = true;