Replaces the Angular 18 app with Next.js 16 / React 19 / Tailwind 4 / shadcn,
the same stack and design system as nachklang-feedback, planned in
docs/rewrite-plan.md.
- Admin: all calendars in one mobile-friendly list (month groups, calendar
chips, Kommend/Vergangen/Alle, search, sort, filters in the URL), an edit
sheet for create/edit/duplicate/delete, publish confirmation, and an
"Abonnieren" dialog with subscription links for every calendar.
- Public landing page: subscribe links from env instead of hardcoded, plus
the next public events, server-rendered and revalidated every 5 minutes.
- All times handled explicitly as Europe/Berlin; whole-day events stored as
00:00-23:59. Fixes carried over from the Angular app: the move dialog
leaking a cancelled calendar change, saves that looked saved when they
failed, in-place Date mutation, and duplicated calendar-id mappings.
- Same shared-session auth as before (proxy.ts gate, /admin/me, 401 vs 403).
- 112 Vitest tests over lib/; docs in docs/ (architecture, features,
gotchas, API wish list, deployment).
Needs the API branch feature/calendar-ical-escaping-subscriptions deployed
first (GET /calendar/events/subscriptions).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
