Refactor code structure and dependencies

- Remove unused files and modules
- Update submodule URL for epess-database
- Update DATABASE_URL in compose.yaml
- Update CI workflow to fetch submodules during checkout and fix GITHUB_TOKEN issue
- Enable strict mode in tsconfig.json
- Add UsersService and UsersResolver in users module
- Remove AppService and AppController
- Update main.ts to remove unused imports and log statement
- Add PrismaModule and PrismaService
- Add PrismaContextMiddleware
- Update GraphQL module to use schema and PrismaService
- Update package.json dependencies and devDependencies

src/app.module.ts

@@ -1,8 +1,11 @@
 import { Module } from '@nestjs/common';
 import { GraphqlModule } from './graphql/graphql.module';
 import { PrismaModule } from './prisma/prisma.module';
+import { UsersModule } from './users/users.module';
 
 @Module({
-  imports: [PrismaModule, GraphqlModule],
+  imports: [
+    GraphqlModule,  // GraphQL setup
+  ],
 })
 export class AppModule {}