curl "https://api.nedzo.ai/v1/workspaces/19c3b12f-ec54-43ad-8686-00e921f1befd/billing/usage?startDate=2026-04-01T00:00:00Z&endDate=2026-05-01T00:00:00Z" \
    -H "Authorization: Bearer YOUR_API_KEY"

{
  "workspaceId": "19c3b12f-ec54-43ad-8686-00e921f1befd",
  "startDate": "2026-04-01T00:00:00Z",
  "endDate": "2026-05-01T00:00:00Z",
  "currency": "usd",
  "totalSpendCents": 8500,
  "totalTopupCents": 20000,
  "totalRefundCents": 0,
  "totalAdjustmentCents": 1500,
  "byType": {
    "usage": -8500,
    "topup": 20000,
    "refund": 0,
    "adjustment": 1500
  }
}