refactor: migrate API from Apollo Server to Mercurius and enhance GraphQL implementation

- Replaced Apollo Server with Mercurius for GraphQL API
- Updated resolvers to use Mercurius-compatible GraphQL implementation
- Migrated from Express to Fastify for server framework
- Improved error handling with GraphQL error extensions
- Added Zod for environment variable validation
- Updated Prisma schema and migrations
- Configured CORS and WebSocket subscriptions
- Simplified GraphQL schema and resolver structure
- Enhanced type safety and code organization

.gitignore

@@ -25,12 +25,8 @@ coverage
 .next/
 out/
 build
-dist/
+dist
 
-# Prisma
-apps/api/prisma/migrations/
-apps/api/prisma/dev.db
-apps/api/prisma/dev.db-journal
 
 # Debug
 npm-debug.log*