feat: Build DAU/MAU chart widget (frontend)

[Ummi-001]

Closes #572

Summary

Adds a DAU/MAU chart widget to the analytics dashboard, per issue #572.

Changes

• frontend/lib/api/analyticsApi.ts — new analytics API client (getDauMauMetrics) that fetches DAU/MAU time series data from the backend analytics endpoint.
• frontend/components/analytics/DauMauChart.tsx — new chart component rendering DAU and MAU as a line chart (recharts), with:
  • A date-range picker (presets for 7/30/90 days, plus custom start/end date inputs) that re-fetches data on change.
  • A stickiness ratio callout (average DAU/MAU %).
  • Loading, error, and empty states.
• frontend/app/analytics/page.tsx — new /analytics page that renders the chart.
• Added recharts as a dependency for chart rendering.

Notes

• Data fetching uses @tanstack/react-query, which is already wired up in the app via QueryProvider.
• The client currently calls GET /analytics/dau-mau?startDate=...&endDate=.... The backend analytics module (backend/src/analytics/) doesn't yet expose this endpoint — only the entity and event listener exist so far. Once the backend endpoint lands, only analyticsApi.ts should need adjusting if the route or response shape differs.

[vercel]

@Ummi-001 is attempting to deploy a commit to the aminubabafatima8-gmailcom's projects Team on Vercel.

A member of the Team first needs to authorize it.

[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

Project	Deployment	Actions	Updated (UTC)
mind-block-app-frontend	Ready	Preview, Comment	Jul 21, 2026 1:51pm

[phertyameen]

great!