Getusagesummary
Daily-aggregate KPIs for the window plus an equal-length **previous** window for comparison.
**Success `data`:** `preset`, `window`, `previousWindow`, `current`, `previous` (rollup rows).
**Example `data` (shape):**
```json
{
"preset": "30d",
"window": { "startDate": "2026-01-01", "endDate": "2026-01-30" },
"previousWindow": { "startDate": "2025-12-02", "endDate": "2025-12-31" },
"current": { "request_count": "...", "cost_sum": "..." },
"previous": { "request_count": "...", "cost_sum": "..." }
}
```