Phase 5: ship the catalog ActiveAdmin resources from the engine

- the 7 catalog admin files (softwares, releases, external_links,
  platform_links, images, files page, downloads) move to the engine's
  app/admin; the host ActiveAdmin instance loads them via
  ActiveAdmin.application.load_paths (single admin, URLs unchanged)
- engine initializers: Zeitwerk ignore for app/admin (production eager load)
  and load_paths + watchable_dirs registration, guarded by defined?(ActiveAdmin)
  so the admin-less dummy app boots
- images admin reads image owners from WarpEngine.config.image_owners; the
  host registers the Member owner in config/initializers/warp_engine.rb;
  the interim ImageUsage registry is gone
- fix: SoftwareImage.distinct.pluck clashed with its order(:position)
  default scope on MySQL (unscope(:order)) — introduced in phase 0, caught
  by the first authenticated /admin/images smoke test
- files page: download links use the public /file/ URL instead of the raw
  container path; the picker's stored path comes from config

Verified: both suites green, zeitwerk:check (production) clean, JSON
baselines intact, authenticated admin smoke test on every page incl.
the 3-level nested software form and Files picker mode.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

lib/warp_engine/engine.rb

@@ -1,5 +1,22 @@
 module WarpEngine
   class Engine < ::Rails::Engine
     isolate_namespace WarpEngine
+
+    # Az app/admin fájlok ActiveAdmin DSL-t tartalmaznak, nem definiálnak a
+    # fájlnévnek megfelelő konstansokat — a Zeitwerk (eager load) nem nyúlhat hozzájuk.
+    initializer "warp_engine.ignore_admin_dir", before: :setup_main_autoloader do
+      Rails.autoloaders.main.ignore(Engine.root.join("app/admin"))
+    end
+
+    # Az admin erőforrásokat a HOST ActiveAdmin példánya tölti be; az engine csak
+    # regisztrálja a saját app/admin könyvtárát. Auth/téma/route-ok a host dolga.
+    initializer "warp_engine.active_admin" do |app|
+      if defined?(ActiveAdmin)
+        admin_dir = Engine.root.join("app/admin").to_s
+        ActiveAdmin.application.load_paths << admin_dir
+        # dev módban az engine admin-fájljainak szerkesztése is triggerel reloadot
+        app.config.watchable_dirs[admin_dir] = [ :rb ]
+      end
+    end
   end
 end