feature: support Postgres 18

<!-- This is an auto-generated comment: release notes by coderabbit.ai --> ## Summary by CodeRabbit * **New Features** * Added support for PostgreSQL 18, including version detection and tooling integration. * Expanded allowable database version configuration to include 18 (migration included). * **Documentation** * Updated feature list to reflect PostgreSQL 18 support. * **Chores** * Extended dependency checks to verify PostgreSQL 18 client tools (psql and pg_dump). * Updated Docker images/builds to install PostgreSQL 18 client. <!-- end of auto-generated comment: release notes by coderabbit.ai -->