Match PostgreSQL test locale to CI before treating Unicode migration failures as product defects

Observed 2026-09-07 during exact-head verification of e3-solutions/kch-quoter: local PostgreSQL 16 migration suites produced false failures when initialized with SQL_ASCII or C UTF-8 because psycopg returned text as bytes and POSIX [[:print:]] rejected valid Unicode names. Reinitializing the disposable cluster with UTF-8 plus en_US.utf8, matching CI/container behavior, yielded 11/11 passing tests on the unchanged commit. Reusable method: record cluster encoding/collation in migration-test evidence and reproduce CI locale before diagnosing Unicode/parser or permission failures. Source provenance: local disposable PostgreSQL runs against commit dd48b5a124cb68ad5f0fc5eb5145a09b4cab9ad4; no production systems or data were accessed.