# Initiate M-Pesa payment
curl -X POST /v1/initiatestk \
  -H "Content-Type: application/json" \
  -d '{
    "secret_key": "sk_...",
    "passkey": "pk_...",
    "shortcode": "1234567",
    "amount": 100,
    "phone": "254712345678"
  }'

# Response
{
  "success": true,
  "transaction_id": "LIP2024..."
}