Phase 3: move service layer, serializers and DTOs into WarpEngine + dummy-app test suite

- all catalog services (update/software/highlighted/builds/file/file-manager/
  download/image + SoftwareResponseBuilder), the SoftwareUpdater platform
  services and their concerns, Blueprinter serializers (incl. TimestampFields)
  and the 4 DTOs now live in the engine under WarpEngine::
- constantize dispatch strings use absolute names
  (WarpEngine::SoftwareUpdater::<Platform>Service)
- container paths read from WarpEngine.config everywhere (FileService,
  DownloadService, FileManagerService, ArchiveExtraction, ReleaseSerializer
  path rewriting); FileManagerService base path is now lazy
- engine requires blueprinter itself; gemspec declares blueprinter + rubyzip
- engine test suite: spec/dummy app (mysql warp_engine_test, catalog-only
  schema), rails_helper with engine-local factories; catalog model/service
  specs and factories moved from the host
- host suite keeps TTG specs and loads catalog factories from the engine

Verified: engine suite 40 green, host suite 14 green, /api/software and
/api/builds byte-identical to baselines, admin OK.

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

spec/rails_helper.rb

@@ -0,0 +1,31 @@
+require "spec_helper"
+ENV["RAILS_ENV"] ||= "test"
+require_relative "dummy/config/environment"
+
+abort("The Rails environment is running in production mode!") if Rails.env.production?
+require "rspec/rails"
+
+begin
+  ActiveRecord::Migration.maintain_test_schema!
+rescue ActiveRecord::PendingMigrationError => e
+  abort e.to_s.strip
+end
+
+# A factory_bot_rails a dummy app gyökerében keresne; a factory-k az engine spec/ alatt élnek
+FactoryBot.definition_file_paths = [ File.expand_path("factories", __dir__) ]
+FactoryBot.reload
+
+RSpec.configure do |config|
+  config.use_transactional_fixtures = true
+  config.infer_spec_type_from_file_location!
+  config.filter_rails_from_backtrace!
+
+  config.include FactoryBot::Syntax::Methods
+end
+
+Shoulda::Matchers.configure do |config|
+  config.integrate do |with|
+    with.test_framework :rspec
+    with.library :rails
+  end
+end