Add server-side visit analytics collection, a public-page ping endpoint,
and a full-screen AnalyticsView for admins.
Backend:
- Add pagerite/analytics.py: Analytics/Visit model, Store, and persistence
- Wire /_a ping endpoint and GET /_api/analytics into pagerite/app.py
Frontend:
- Add full-screen AnalyticsView with visitor charts and transition map
- Add VisitorCharts and TransitionGraph subcomponents
- Add analytics JS helpers in frontend/src/analytics/
- Send navigation pings from frontend/src/pagerite.js
- Mount AnalyticsView from frontend/src/main.js
- Document the feature in docs/analytics.md and update AGENTS.md