warp_engine: load ActiveJob itself so production eager load works

The engine ships an ActiveJob based job (PipelineSyncJob), but a host's
application.rb does not necessarily require active_job/railtie - apps/api does
not. With eager loading off (development, test) nothing noticed; in production
WarpEngine::ApplicationJob blew up with "uninitialized constant
WarpEngine::ActiveJob", which is exactly what `rails zeitwerk:check` in
RAILS_ENV=production reported. An engine that ships jobs has to pull in the
framework it needs, so lib/warp_engine.rb requires the railtie.

Pre-existing on 0.1.0 as well; found while verifying that the 0.2.0 changes do
not break the portal. All three api-test steps are green now.

apps/api Gemfile.lock follows the 0.1.0 -> 0.2.0 path gem bump.

lib/warp_engine.rb

@@ -1,3 +1,9 @@
+# Az engine ActiveJob-ra épülő jobot szállít (PipelineSyncJob), ezért a
+# framework betöltése a mi dolgunk: a host application.rb-je nem feltétlenül
+# require-öli az active_job/railtie-t, és eager loadnál (production) a
+# WarpEngine::ApplicationJob különben uninitialized constant-tal elszáll.
+require "active_job/railtie"
+
 require "blueprinter"
 require "apipie-rails"