NEAR AI Cloud: Get organization usage broken down by model.

/api-reference/openapi.json get /v1/organizations/{org_id}/usage/by-model Returns one row per model, summed over a rolling window ending now: day = last 24h, week = last 7 days, month = last 30 days (NOT calendar day/week/month-to-date). Used by the dashboard pie chart to show which models drive spend.