Migrate docs deployment workflow from Poetry to uv

[amc-corey-cox]

Summary

• Replace Poetry with uv in the docs deployment workflow
• Update actions to current versions (checkout@v4, setup-uv@v3, github-pages-deploy-action@v4)
• Remove mysterious token.txt write that was leaking GITHUB_TOKEN into the source tree during builds

Closes #180

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 65.63%. Comparing base (0081d75) to head (b645ee3).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #302   +/-   ##
=======================================
  Coverage   65.63%   65.63%           
=======================================
  Files           5        5           
  Lines         227      227           
=======================================
  Hits          149      149           
  Misses         78       78           

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[Copilot]

Pull request overview

Migrates the GitHub Actions docs deployment workflow away from Poetry and onto uv, while updating action versions and removing a step that wrote GITHUB_TOKEN into the working tree during doc builds.

Changes:

• Switch docs workflow dependency management and command execution from Poetry to uv.
• Update GitHub Actions used in the workflow (e.g., actions/checkout@v4, setup-uv@v3, github-pages-deploy-action@v4).
• Remove the workflow step that wrote secrets.GITHUB_TOKEN into src/dm_bip/token.txt.

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