curl -X POST "https://olive-gateway-a6ba.onrender.com/api/v1/pos/refund" \
  -H "Authorization: Bearer olive_live_xxx" \
  -H "Content-Type: application/json" \
  -d '{
    "original_transaction_id": "txn_pos_12345",
    "amount": "1500.00",
    "reason": "Customer returned item",
    "initiated_by": "admin_user_01",
    "pin": "9999"
  }'

{
  "success": true,
  "message": "Refund processed successfully",
  "refund_id": "rfnd_abc789",
  "original_transaction_id": "txn_pos_12345",
  "refunded_amount": "1,500.00 SLE",
  "timestamp": "2025-01-20T15:00:00Z"
}