Introduce pre-computed daily usage rollups from sandbox_metrics_snapshots.
An hourly background worker aggregates completed days, while today's
usage is computed live from snapshots at query time for freshness.
Backend: new daily_usage table, rollup worker, UsageService, and
GET /v1/capsules/usage endpoint with date range filtering (up to 92 days).
Frontend: replace Usage page placeholder with bar charts (Chart.js),
summary total cards, and preset/custom date range controls.
pptx704
92aab09104