curl https://api.v2.dealmachine.com/v1/mail/campaigns/a1b2c3d4-e5f6-7890-abcd-ef1234567890 \
  -H "Authorization: Bearer dm_sk_live_xxx"

{
  "data": {
    "id": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
    "organization_id": 42,
    "name": "Spring Seller Campaign",
    "status": "active",
    "type": "one_off",
    "total_recipients": 150,
    "total_sent": 120,
    "total_delivered": 115,
    "steps": [{
      "id": "1",
      "step_order": 1,
      "design_id": "design-uuid-123",
      "delay_days": 0,
      "repeat_count": 1
    }],
    "created_at": "2026-03-01T14:23:45Z",
    "launched_at": "2026-03-02T10:00:00Z"
  }
}

{
  "error": {
    "code": "campaign_not_found",
    "message": "Campaign not found",
    "request_id": "req_abc123"
  }
}