api: audit all api interfaces for type safety and null/optional correctness

[MathiasDevelopes]

We currently have no official documentation for this API. All API TypeScript interfaces were generated by reverse-engineering network responses and converting JSON into zod schemas.

This approach does not cover all scenarios: fields that exist in my session may not exist for other users, or may return null/undefined.

As a result, our current type definitions are not fully safe, and runtime errors can occur when unexpected missing or null values appear.

Note

If you want to contribute on making the API more type safe, please post any JSON that breaks the conformity of the current interfaces, and the corresponding API endpoint.
PLEASE CENSOR ANY PERSONAL INFORMATION FROM THE JSON RESPONSE

[MathiasDevelopes]

We provide better data validation in commit 0edf105 by using Zod for runtime data validation.
However, the API can still return unexpected or incorrect data.