Fix NSO Galactic mode controller name collision

[scotwells]

Summary

• Give the Galactic NetworkInterface controller a distinct controller-runtime name.
• Fix NSO cell manager startup with galactic.enabled: true during the staging API-group migration.

Staging evidence

At 2026-10-16 18:03 UTC, a restarted central staging NSO pod exited with controller with name networkinterface already exists. The prior pod remains healthy after rolling back the restart. East was not restarted.

Verification

• go test ./internal/galactic/controller ./internal/cmd/cell
• Resume staging rollout after the fixed NSO image publishes; restart NSO one cell at a time and verify status.attachmentRef.apiGroup becomes galactic.datumapis.com.