curl -X POST "https://app.talkover.ai/api/v1/credits/purchase" \
  -H "Authorization: Bearer your_user_session_token" \
  -H "Content-Type: application/json" \
  -d '{
    "amount": 100.00,
    "payment_method_id": "pm_uuid_1"
  }'

{
  "success": true,
  "data": {
    "amount_charged": 100.00,
    "currency": "USD",
    "new_balance": 250.00,
    "transaction_id": "txn_uuid_1"
  }
}

{
  "success": false,
  "message": "Payment method declined",
  "code": "PAYMENT_FAILED"
}