"""FC-5 migration tooling.

One module per concern (gs/ir/overlap/ml_queue/verify/cleanup).
Each migrator returns a counts dict; the run_migration task wires
that dict into MigrationRun.counts so the UI polling shows progress.

backup + rollback were retired in FC-3h (2026-05-24); first-class
backup lives at backend/app/services/backup_service.py and exposes
its own /api/system/backup/* surface.
"""