Postgres adapter for PropertyReferenceReader: selects landlord_property_id and
uprn from the property table for a portfolio, feeding PropertyUprnLookup. Thin
I/O over the FE-owned property table; exercised end-to-end where a DB is
available (no DB in this environment).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>