curl --request GET \
  --url https://alpa-sistema-api.onrender.com/api/referral/stats \
  --header 'Authorization: Bearer <token>'

{
  "totalReferrals": 123,
  "completedReferrals": 123,
  "pendingReferrals": 123,
  "totalFixedRewards": 123,
  "totalFixedRewardAmountCents": 123,
  "totalCommissions": 123,
  "totalCommissionAmountCents": 123,
  "totalRewards": 123,
  "totalRewardAmountCents": 123,
  "totalWithdrawnCents": 123,
  "availableBalanceCents": 123
}