fix: harden runtime offers and catalog editor for 4.3.3

[BrannonSD]

Summary

• Repair runtime-price generation so it emits the exact 50–5000 V-Bucks domain in 50-V-Buck increments with bounded expression depth.
• Remove obsolete dynamic RuntimePrice members/parameters and qualify generated runtime option types with the configured Offers module.
• Correct runtime validation syntax and expand integration-contract coverage for primary, alternate, and bundle runtime paths.
• Fix country-flag atlas rendering, modal overflow containment, and native select focus styling across catalog editors.
• Add a real hidden Electron/DOM regression gate without screenshots.
• Record the flat-cartoon UTM_Demo icon prompts/output provenance and bump the release metadata to 4.3.3.

Verification

• npm run test:all green after the version bump (276 JS tests, 19 Python tests, desktop lifecycle, distribution, and portable updater checks).
• npm run test:ui-renderer green without capturing screenshots.
• UTM_Demo temporary acceptance catalog applied through guarded UTM MCP, compiled through the real UEFN Workflow Server and Epic BuildAll, then restored hash-for-hash to its original catalog/files.

Native Texture2D adoption was not re-run because the live UEFN connector heartbeat was stale; existing controlled project icon assets were retained and the catalog-only acceptance path was used.