Create live dashboard for GrantFox campaign metrics

## Description
Dashboard tracking GrantFox campaign performance metrics.

## Requirements
- Contributor application rate
- Issue completion rate
- PR quality score trend
- Campaign ROI metrics
- Contributor leaderboard

## Files to Touch
- analytics/app/grantfox-metrics/page.tsx
- analytics/components/CampaignDashboard.tsx

**Complexity: 200 points**