Add the Hibernate unique constraint on STM_GEOINFO.GEO_STYID #94

The Hibernate reference declares a unique constraint that production Liquibase does not. Hibernate ddl-auto=validate still starts. This row is INFO, not PROBLEM.

Measured 2026-10-19 with bash tools/scripts/compare-schema-drift.sh both --against jpa --fail-on none. Both dialects:

• STM_GEOINFO UK GEO_STYID only on the Hibernate reference

That is the only constraint_only_reference row in the report.