POST Supprimer plusieurs contacts

POST /api/v1/contacts/bulk-delete

{
  "data": {
    "requested": 2,
    "deleted": 1,
    "notFound": ["cnt_missing"]
  }
}

{
  "data": {
    "mode": "async",
    "jobId": "job_abc123",
    "status": "pending",
    "operation": "bulk_delete_contacts",
    "requestedCount": 900,
    "progress": 0,
    "message": "Bulk operation queued. Check status via GET /api/contacts/bulk-jobs/job_abc123"
  }
}