chore: update dependencies and improve GraphQL schema preparation

- Updated eslint to version 9.36.0
- Updated jest and jest-cli to version 30.1.3
- Updated npm-check-updates to version 18.3.0
- Updated tsx to version 4.20.5
- Added a promise-based mechanism to prevent multiple preparations of the GraphQL schema in service.js
- Implemented a test case to verify that the GraphQL schema is not prepared multiple times concurrently

Author: icebob