- Add POST /api/v1/check-in endpoint with CheckInSubmission
- nearby_cafes returns HTML fragment for Datastar, JSON for API
- Add NearbyCafeView and NearbyCafesFragment for server-rendered results
- Rewrite checkin.html: replace checkin.js with Datastar signals,
@post for submission, @get for nearby search, inline geolocation JS
- Cafe filtering uses data-show with signal-based search
- Add home page at / with scan, last brew, open bags, activity, stats
- Add check-in page at /check-in with cafe search + roast scan + rating
- Use Datastar signals for check-in UI state (steps, rating, selection)
- Bridge async JS (geolocation, fetch) to Datastar via custom events
- Replace nav camera icon with house icon (always visible)
- Redirect /scan to / for backward compatibility
- Delete scan.html, add home.html, checkin.html, checkin.js
