feat: implement orchestrated auto-update system and fix deployment

- Add sma user module to little-rascal configuration for passwordless deployment
- Replace cosmic-greeter with greetd on both congenital-optimist and little-rascal
- Implement staggered auto-update system that updates remote machines first
- Add proper SSH user configuration for secure deployments
- Fix deployment permission issues by configuring admin user access
- Ensure orchestrator machine (congenital-optimist) reboots last to prevent SSH disconnection
- Add comprehensive error handling and update reporting
- Successfully tested lab tool deployment and auto-update on all machines

Fixes the critical issue where orchestrator reboot could break SSH connections
during multi-machine updates.

modules/desktop/cosmic.nix

@@ -1,11 +1,14 @@
-{ config, pkgs, ... }: {
+{
+  config,
+  pkgs,
+  ...
+}: {
   # Cosmic Desktop Environment (System76's new Rust-based DE)
   services.desktopManager.cosmic.enable = true;
-  services.displayManager.cosmic-greeter.enable = true;
   services.desktopManager.cosmic.xwayland.enable = true;
-  
+
   # Cosmic-specific packages
   environment.systemPackages = with pkgs; [
     # Cosmic is still in development, most packages come with the DE
   ];
-}
+}