Add TypeScript types for auth

**Problem**
When working with api, the error messages could be more descriptive.

**Suggestion**
Improve error handling and add detailed error messages.

**Context**
This would help with debugging and maintenance.

Start by locating the TypeScript authentication API types and the current API error-handling entry point. Clarify which authentication responses and error cases are in scope, then verify that the types are exposed and the resulting errors include more descriptive debugging information.

Written by the indexing model from the issue text.