Stop/Start an import

Change runtime mode for an active import (pause, resume, terminate).

Use this endpoint when operators need to control long-running import processing.

Mode rules:

• pause: allowed only for active imports.
• resume: allowed only when status is PAUSED.
• terminate: blocked for already completed/failed/terminated imports.

Behavior:

• Applies the mode to all underlying batch workflows.
• Persists the new import status.
• Returns 400 when the requested transition is invalid.