Rewrite with new stack

[muety]

Preferred option: Astro + Pocketbase.

• Use Pocketbase backend-as-a-service for data storage
• Build event pages as static HTML files with astro
  • Fetch events data from backend during build
• Build dynamic endpoints with SSR for reading and writing comments and reviews from backend
• User login / signup directly against Pocketbase (use API rules to restrict to KIT e-mails)
• Implement file uploads (see #26) with Pocketbase too