migrate away from supabase to atproto #8

The application's reliance on a cloud service should at the very most be reliant on just where to host (like a "deploy-anywhere" container), not on SaaS products. Supabase is also a bit annoying to use.

• remove supabase-specific scripts in app/package.json
• remove app/src/supabase/
• remove app/src/generated/database.types.ts
• remove app/src/lib/supabaseClient.ts
• remove supabase-specific types in app/src/app.d.ts
• deps: remove @supabase/ssr, @supabase/supabase-js
• rename app/ to appview/
• switch away from Supabase Auth (figure out ATProto+OAuth stuff)
  • e.g use Better-Auth and find an existing OAuth ATProto provider (or follow their official guide to writing a custom one)
• any other things to remove..