Create a feasibility analysis

Runs the v1 deterministic feasibility pipeline for a site reference or location input, persists the result, and returns the analysis snapshot. Authentication is optional for non-polygon inputs; polygon geometry and polygon-resolved sites require a Supabase bearer JWT and return AUTH_REQUIRED when missing. Parcel owner details and assessment/sale data (site.selectedParcel.ownershipHint and rawCityData) are returned only to authenticated callers; anonymous responses null those fields. The route accepts an Idempotency-Key header for safe retries, uses the PUBLIC_READ_HEAVY route bucket behind the PUBLIC_API middleware backstop, and returns registered v1 error codes including INVALID_REQUEST, AUTH_REQUIRED, RATE_LIMITED, and ANALYSIS_FAILED.