Hubuum client library (Rust): Authenticated requests may escape the configured base path through redirects

Summary

## Impact

The built-in async and blocking clients used reqwest's default redirect policy. `BaseUrl` constrains the initial request to the configured origin and path prefix, but redirect processing occurs after that validation. reqwest retains sensitive headers when a redirect changes only the path on the same scheme, host, and port. A redirect from a Hubuum endpoint to another path on a shared origin could therefore carry the bearer `Authorization` header outside the configured Hubuum path prefix.

Exploitation requires an attacker, compromised server, or intermediary to influence a 3xx response. Cross-origin redirects are not affected because reqwest strips sensitive headers when scheme, host, or port changes.

## Patches

Version 0.6.1 configures both built-in HTTP clients with `reqwest::redirect::Policy::none()`. Redirect responses are returned as 3xx API errors instead of being followed. Supplying a preconfigured reqwest client remains an explicit opt-in to that client's redirect policy.

## Workarounds

On affected versions, construct a reqwest client with `reqwest::redirect::Policy::none()` and pass it through `with_http_client`. Deployments can also reduce exposure by ensuring the Hubuum origin is not shared with other applications and that trusted infrastructure never redirects API requests outside the configured path prefix.