curl -X POST "https://demo.api.vultlocal.com/api/v1/subscribers/sub_abc123/verify-pin" \
  -H "Authorization: Bearer olive_live_xxx" \
  -H "Content-Type: application/json" \
  -d '{
    "pin": "1234"
  }'

{
  "success": true,
  "message": "PIN verified successfully"
}

{
  "success": false,
  "message": "Invalid PIN",
  "attempts_remaining": 2
}

{
  "success": false,
  "message": "Account locked due to too many failed attempts",
  "locked_until": "2025-01-20T16:00:00Z"
}