Migrate from Prisma to Supabase Client (Cursor Prompt)

Migrate this project from Prisma ORM to the Supabase JavaScript client.

STEPS:
1. Read the existing prisma/schema.prisma to understand the data model.
2. Create equivalent Supabase tables using SQL migrations in supabase/migrations/. Map Prisma types to PostgreSQL types.
3. Generate TypeScript types from the Supabase schema using: npx supabase gen types typescript.
4. Create src/lib/supabase/client.ts and src/lib/supabase/server.ts if they don't exist.
5. For every file that imports from '@prisma/client', replace Prisma queries with Supabase equivalents:
   - prisma.user.findMany() -> supabase.from('users').select('*')
   - prisma.user.findUnique({ where: { id } }) -> supabase.from('users').select('*').eq('id', id).single()
   - prisma.user.create({ data }) -> supabase.from('users').insert(data)
   - prisma.user.update({ where, data }) -> supabase.from('users').update(data).eq('id', id)
   - prisma.user.delete({ where }) -> supabase.from('users').delete().eq('id', id)
   - Include/relation queries -> use .select('*, posts(*)') for joins
6. Add RLS policies for each table based on the existing access patterns.
7. Remove Prisma dependencies: @prisma/client, prisma. Delete prisma/ directory.

DO NOT:
- Change the API response shapes — keep the same data structure
- Modify frontend components
- Change environment variable names (add new ones alongside existing)

ENVIRONMENT VARIABLES TO ADD:
- NEXT_PUBLIC_SUPABASE_URL
- NEXT_PUBLIC_SUPABASE_ANON_KEY
- SUPABASE_SERVICE_ROLE_KEY