curl -X GET "https://olive-gateway-a6ba.onrender.com/api/v1/agents/agent_abc123/balance" \
  -H "Authorization: Bearer olive_live_xxx"

{
  "success": true,
  "agent_id": "agent_abc123",
  "business_name": "ABC Money Services",
  "balance": 150000000,
  "balance_formatted": "1,500,000.00 SLE",
  "currency": "SLE",
  "last_transaction_at": "2025-01-15T10:30:00Z"
}