JupyterHub authentication support for Cuiman

[forman]

Cuiman now supports JupyterHub authentication in Python, the CLI, and the launched app. On a suitably configured Hub, users can access their processing service without copying or managing tokens themselves.

• auto is the default for new configurations. It discovers authentication—currently JupyterHub only—and uses anonymous access if none is detected.
• jupyter requires JupyterHub authentication and reports an error if unavailable.
• none skips discovery and uses anonymous access. Existing profiles explicitly selecting none keep this behavior.

Python and app requests use the current token supplied by JupyterHub. Authentication failures stop requests instead of continuing anonymously. Tokens stay out of the app browser, and Cuiman logout does not sign users out of JupyterHub.

Closes #211.

Checklist (strike out non-applicable):

• Changes documented in CHANGES.md
• Related issue exists and is referred to in the PR description and CHANGES.md
• Added docstrings and API docs for any new/modified user-facing classes and functions
• Changes/features documented in docs/*
• Unit-tests adapted/added for changes/features
• Test coverage remains or increases (target 100%)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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