US3 - Rule Management:
- Backend: CRUD API + activate/deactivate + test against 90d history
- Frontend: RuleList sidebar, RuleForm (create/edit), RuleTestResults
- Weight/threshold sliders, condition type selector, audit logging
US4 - Dashboard:
- Backend: GET /dashboard/metrics (24h/7d/30d/90d), CSV export
- Frontend: MetricCards, alerts-by-hour bar chart, status pie chart,
top rules horizontal bar chart via Recharts
Stack: 20 API routes total. Frontend tsc clean, vite build passes.