Update justfile to use nixos-rebuild-ng by default

devshells/satellite.nix

@@ -1,10 +1,11 @@
-{ pkgs, ... }:
+{ pkgs, upkgs, ... }:
 pkgs.mkShell {
-  packages = with pkgs; [
-    just
-    python3
-    sops
-    ssh-to-age
-    age
+  packages = [
+    pkgs.just # script runner
+    pkgs.python3 # used throughout a bunch of just recipes
+    pkgs.sops # just sops-rekey
+    pkgs.ssh-to-age # just ssh-to-age
+    pkgs.age # just age-public-key
+    upkgs.nixos-rebuild-ng
   ];
 }