PostgreSQL migration orchestrator for HephaestusOban.Migration.
This module applies versioned migration steps (V01, V02, V03, ...)
and records the latest applied version in the hephaestus_step_results
table comment, following the same version-tracking pattern used by Oban.
up/1 applies only the missing versions up to the requested target.
down/1 rolls back from the current version down to the requested target.