PostgreSQL migration orchestrator for HephaestusEcto.
This module coordinates versioned migration modules (V01, V02, and so on) and keeps the
applied schema version in a comment on the workflow_instances table. The public
HephaestusEcto.Migration module delegates here for all up/1, down/1, and
migrated_version/1 calls.
The orchestrator pattern keeps each schema change isolated in its own module while still exposing a stable, version-aware API to host applications.