feat(emacs): robust Nix-based Emacs setup with daemon service, improved elisp dev, and full package documentation

- Emacs daemon runs as a systemd service via Nix
- Modular Emacs config with Nix-managed packages (elisp-slime-nav, aggressive-indent, highlight-defined, etc.)
- Keybinding fixes and error handling improvements
- New EMACS_README.md explains ecosystem and troubleshooting
- Nix config: GUI sudo askpass, podman, and desktop tweaks
- All errors from missing packages and keybindings resolved

modules/desktop/common.nix

@@ -26,6 +26,14 @@
   environment.systemPackages = with pkgs; [
     firefox
   ];
+  
+  # GUI sudo askpass helper for desktop environments
+  programs.ssh.askPassword = "${pkgs.libsForQt5.ksshaskpass}/bin/ksshaskpass";
+  security.sudo.extraConfig = ''
+    Defaults env_keep += "SSH_ASKPASS"
+  '';
+  environment.variables.SUDO_ASKPASS = "${pkgs.libsForQt5.ksshaskpass}/bin/ksshaskpass";
+  
   # Flatpak support
   services.flatpak.enable = true;
 }