Integrate GraphQL into backend

The old stack used a separate NodeJS application for the GraphQL API. This was because I was learning how to do GraphQL and followed a tutorial that stepped through making a common GraphQL database shim.

Now with more advanced knowledge, the GraphQL API endpoint should be integrated into the app itself. This way separate stacks don't have to be deployed alongside this backend, regardless of the simplicity of the backend. Additionally, we can then unify the web-app's data transmission relying only on GraphQL in the far future.

- [x] Research GraphQL python libraries ([strawberry](https://github.com/strawberry-graphql/strawberry) looks great!)
- [x] Backend refactor
- [x] Class layout
- [ ] GraphQL server in python backend
- [ ] Use GraphQL for real-time updates
- [ ] Abolish legacy websocket endpoint

该 issue 描述了将 GraphQL 服务器集成到现有 Python 后端中，以替换一个独立的 NodeJS 应用程序。研究其中提到的 strawberry 库，并检查当前的后端结构，以了解类的布局和现有的 websocket endpoint。目标是实现 GraphQL 服务器，并最终将其用于实时更新，同时移除 legacy websocket。

由索引模型根据 Issue 内容生成。