[FE-39] Build /admin/stats page — charts for submissions, risk distribution, verification rate

[mftee]

Overview

Administrators need an analytics dashboard to understand platform usage trends and the health of the document pipeline. This page visualises the aggregate stats from GET /api/admin/stats (BE-72) as charts and KPI cards.

Background

File to create: frontend/app/(protected)/admin/stats/page.tsx

Access: Admin role only

Charts:

1. Document submissions over time — line chart (last 30 days, one data point per day)
2. Risk flag distribution — horizontal bar chart showing how often each flag is triggered
3. Document status distribution — donut chart (PENDING / VERIFIED / FLAGGED / REJECTED)
4. Verification success rate — gauge showing % of anchor jobs that succeeded

KPI cards (top row):

• Total documents, Total users, Avg risk score, Verification success rate

Date range filter: Apply to all charts simultaneously

Acceptance Criteria

• All charts rendered using Recharts (already installed) or equivalent
• Charts are responsive — fit the container width at mobile and desktop breakpoints
• Date range filter applied as query params to GET /api/admin/stats
• KPI cards show sparkline trend (up/down vs. previous period)
• Charts show a loading skeleton while data is fetching

[temisan0x]

Hi Maintainer! I'd love to take on this issue

[temisan0x]

Hi Maintainer! I'd love to take on this issue