DELETE Remove members

DELETE /api/v1/contacts/groups/{groupId}/members

{
  "data": {
    "removed": 1,
    "notInGroup": 1
  }
}

{
  "data": {
    "mode": "async",
    "jobId": "job_def456",
    "status": "pending",
    "operation": "remove_from_group",
    "requestedCount": 280,
    "groupId": "uuid-group",
    "progress": 0,
    "message": "Bulk operation queued. Check status via GET /api/contacts/bulk-jobs/job_def456"
  }
}