Refactor NixOS configuration: Move GUI apps to desktop modules and create headless config

- Move GUI applications from users/jsutter.nix to appropriate desktop modules:
  * office.nix: slack, signal-desktop
  * gaming.nix: discord, stremio
  * plasma.nix: arc-theme, pinentry, tigervnc
  * dev.nix: putty
  * media.nix (new): vlc, deluge

- Create systems/common-headless.nix for server configurations:
  * Remove GUI dependencies (Flatpak, XDG portals, fonts, graphics drivers)
  * Include only essential CLI tools and server packages
  * Disable X server completely

- Simplify skip01 configuration:
  * Remove Intel graphics drivers and OpenGL support
  * Use headless common configuration
  * Keep unified users/jsutter.nix (no split files)

- Update flake.nix to include new media.nix module in desktop systems

Result: Clean separation between desktop and headless configurations
with improved modularity and maintainability.

desktop/dev.nix

@@ -6,6 +6,7 @@ environment.systemPackages = with pkgs; [
    (python3.withPackages(ps: with ps; [ pandas requests python-dotenv pip uv ]))
   nodejs
   rpi-imager
+  putty                   # SSH/Telnet client
   pkgs-unstable.windsurf  # Use windsurf from unstable packages
   ];