List pending invitations

curl 'https://api.expiryedge.com/v1/invitations/pending' \
  -H "Authorization: Bearer $EXPIRYEDGE_API_KEY"

{
  "pending_invitations": [
    {
      "id": "inv_5Rt2kWq",
      "email": "maria@northwinddental.com",
      "organization_id": "org_northwind",
      "invited_by": "u_71bXq",
      "inviter_name": "Dana Brooks",
      "status": "pending",
      "created_at": "2026-09-27T14:05:00.000Z",
      "expires_at": "2026-10-04T14:05:00.000Z"
    }
  ]
}