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>

app/services/warp_engine/software_service.rb

@@ -0,0 +1,11 @@
+module WarpEngine
+  class SoftwareService
+    include SoftwareResponseBuilder
+
+    def index
+      softwares = WarpEngine::Software.includes(releases: [ :release_assets ]).includes(:external_links, :software_images).all
+      counts = download_counts_for(softwares.flat_map { |sw| sw.releases.map(&:id) })
+      { softwares: softwares.map { |sw| build_response(sw, sw.releases.to_a, counts) } }
+    end
+  end
+end