Hub database migrations

The Alembic environment in this directory owns only the ITWorx MCP Hub control database. ContextForge is a separate database/user and is intentionally absent from the metadata import graph.

Development example:

$env:HUB_DATABASE_URL = "sqlite:///./itworx-hub-dev.db"
alembic -c infrastructure/database/alembic.ini upgrade head

Production migrations are forward-only. A destructive rollback is a restore operation after backup and health verification, not an ad-hoc downgrade.