Add GraphQL Support Using HotChocolate

[Apolixit]

As a developer,
I want to integrate HotChocolate into the application,
So that I can expose data via GraphQL queries and mutations efficiently.

Acceptance Criteria:

1. The /graphql endpoint is available and serves a basic schema with at least one query and one mutation.
2. The integration works with the existing ASP.NET Core pipeline.
3. GraphQL queries return data correctly, and mutations perform updates as expected.