Add Microsoft Clarity as a fourth analytics provider option alongside
Umami, Google Analytics, and Custom. Clarity provides free heatmaps,
session recordings, and user analytics.
- admin.types.ts: Add 'clarity' to AnalyticsProvider union type
- api/admin/site/route.ts: Add 'clarity' to validation
- admin/page.tsx: Add Clarity option to dropdown + Project ID input UI
- layout.tsx: Inject Clarity tracking script with project ID