feat(gui): enable docker service on workstation

Imports docker/enable-service.nix and pins virtualisation.docker to
docker_29 via a nixpkgs overlay. Fixes indentation on `imports` block
and `programs.direnv.enable` line so nixpkgs-fmt passes.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

modules/build-types/gui.nix

@@ -1,6 +1,17 @@
 { config, pkgs, lib, inputs, vars, ... }:
 
 {
+  imports = [
+    ../docker/enable-service.nix
+  ];
+
+  nixpkgs.overlays = [
+    (final: prev: {
+      docker = prev.docker_29;
+      docker_cli = prev.docker_29;
+    })
+  ];
+
   environment.systemPackages = with pkgs; [
     inputs.nixos-conf-editor.packages.${pkgs.stdenv.hostPlatform.system}.nixos-conf-editor
     nodejs