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.

apps/api/Gemfile.lock

@@ -1,7 +1,7 @@
 PATH
   remote: ../libs/ruby/warp_engine
   specs:
-    warp_engine (0.1.0)
+    warp_engine (0.2.0)
       apipie-rails
       blueprinter
       rails (>= 8.0)