[e2e-examiner-ui] Examiner: setup authentication for BCeID for e2e testing

## Summary

End-to-end tests for the Examiner web application need a reliable way to obtain and reuse an authenticated session when the scenario requires BCeID (including multi-factor in test and prod; dev bypasses OTP/MFA), using secrets and configuration appropriate for non-production automation.

## Acceptance criteria

- Global setup can authenticate once and persist session state for test workers where the test plan requires BCeID.
- Credentials are supplied only via CI-safe secrets or documented local environment patterns for developers.
- Failure modes are observable in CI logs or artifacts (for example, a clear failure when secrets are missing or auth steps time out).

The issue names no files, tests, or entry points, so first locate the Examiner e2e test configuration and global setup. Trace how authenticated sessions and CI secrets are currently handled before defining the BCeID flow. Done means workers can reuse a session, credentials stay out of source, and missing secrets or timeouts produce clear CI evidence.

Written by the indexing model from the issue text.