PostgreSQL is always needed for vectorsDB regardless of the primary
database. compose/postgresql.yml now only disables MongoDB.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Move MariaDB and PostgreSQL into compose/ overlay files instead of
starting all three databases and switching via env vars. MongoDB stays
in the base compose as the default. CI uses COMPOSE_ENV_FILES at the
job level to load the correct env file per matrix database entry.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>