v0.1.14 — schema sync + gateway in offering schema

• Fully regenerate offering_v1.json from the model: adds gateway to the service_type enum (so usvc_seller data validate accepts it) and drops the stale request_transformer block left by #19.
• Add scripts/generate_schemas.py plus a CI schema-sync job that fails on any drift between the pydantic models and the bundled JSON schemas, preventing the #19/#20 class of bug.

See #21.