Introduces non-server home-manager configs

Allows home-manager configs to be done on a server/non-server basis

Provides an example config by moving emacs to its own space (behind a
lib.optionals so only non-server machines accept it)

marks artemision and rhapsody-in-green as explicitly non-server machines

Signed-off-by: ahuston-0 <aliceghuston@gmail.com>

users/alice/non-server.nix

@@ -0,0 +1,8 @@
+{ pkgs, ... }:
+
+{
+  programs.emacs = {
+    enable = true;
+    package = pkgs.emacs29-pgtk;
+  };
+}