curl -X POST https://api-paycentral.gabondunumerique.com/api/v1/payment/initiate \
  -H "X-Api-Key: sk_sandbox_xxxx" \
  -H "Content-Type: application/json" \
  -d '{
    "amount": 10000, "currency": "XAF",
    "phone": "237691234567",
    "description": "Abonnement Premium",
    "merchant_reference": "SUB-2024-001",
    "callback_url": "https://monsite.cm/webhooks/paycentral"
  }'

{
  "success": true,
  "data": {
    "transaction_id": "01HXYZ9K2JABCDEF",
    "status": "pending",
    "provider": "mtn",
    "amount": 10000,
    "currency": "XAF",
    "fees": 200,
    "net_amount": 9800
  }
}