MaintenanceRepository was built with new over an injected EntityManager
in the readiness probe and in UserCleanupService, outside the container.
MaintenanceModule now provides it, as a factory over the same
context-resolving EntityManager Nest injects everywhere, and both inject
it. The class itself stays free of Nest decorators, like the rest of
src/db, so tests keep building one over their own EntityManager.
No behaviour changes: the probe still pings and the erasure still runs
inside the account deletion's transaction.
Maurice