feat(download): adds auth to support new teehr-hub requirement

[mgdenno]

No description provided.

[Copilot]

Pull request overview

This PR updates the Download client to support teehr-hub’s new authentication requirements (API key / bearer token) and adjusts pagination behavior to follow server-provided links (rel=next) when available. It also adds opt-in local integration testing guidance and markers.

Changes:

• Add api_key / bearer_token configuration and send auth headers on outbound download requests.
• Update pagination to prefer links[rel=next] URLs and allow omitting limit when page_size=None.
• Add local_api pytest marker plus README guidance and new unit/integration tests covering auth + pagination.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
src/teehr/evaluation/download.py	Adds auth header support and next-link pagination logic; updates page sizing defaults to allow server-controlled limits.
tests/download/test_download.py	Adds local_api-marked integration tests and new unit tests for auth headers + pagination behavior.
tests/README.md	Documents how to run opt-in local teehr-hub integration tests and required env vars/markers.
pytest.ini	Registers the new local_api marker.

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[mgdenno]

@samlamont I addressed copilot comments. I think it is pretty good.