DEV: Update engine config to match skeleton

- adds `lib/` autoloading (and removes the plugin.rb workaround)
- adds eager loading of scheduled jobs in development (otherwise they don't work at all)

lib/engine.rb

@@ -4,5 +4,10 @@ module ::DiscourseAi
   class Engine < ::Rails::Engine
     engine_name PLUGIN_NAME
     isolate_namespace DiscourseAi
+    config.autoload_paths << File.join(config.root, "lib")
+    scheduled_job_dir = "#{config.root}/app/jobs/scheduled"
+    config.to_prepare do
+      Rails.autoloaders.main.eager_load_dir(scheduled_job_dir) if Dir.exist?(scheduled_job_dir)
+    end
   end
 end

plugin.rb

@@ -30,8 +30,6 @@ module ::DiscourseAi
   PLUGIN_NAME = "discourse-ai"
 end
 
-Rails.autoloaders.main.push_dir(File.join(__dir__, "lib"), namespace: ::DiscourseAi)
-
 require_relative "lib/engine"
 
 after_initialize do