Add admin-triggered release workflow

[AndreyVMarkelov]

Summary

• add an admin-only Actions button for validated main releases
• run validation, lint, unit tests, documentation, and package checks before creating an annotated vX.Y.Z tag at the exact validated commit
• build final distributions from that immutable tag, verify their version, and upload them as a GitHub artifact
• publish the prebuilt artifacts through a minimal OIDC-only PyPI Trusted Publishing job, then create the GitHub Release
• keep the existing release.created publishing path and document the production release order
• remove the temporary TestPyPI smoke-test path

Validation

• actionlint .github/workflows/pypiupload.yml
• YAML parsed successfully with Ruby Psych
• git diff --check
• production publisher structurally verified to contain only artifact download and pypa/gh-action-pypi-publish@release/v1, with only id-token: write
• confirmed no TestPyPI, AWS, Secrets Manager, stored PyPI credentials, or pip-cache configuration remains
• Ruff check and format check (excluding generated dropbox/_version.py)
• pytest -q test/unit/ — 100 passed
• sphinx-build -b html docs build/html
• synthetic annotated v99.98.97 tag build without a version override
• python -m build
• twine check dist/*
• wheel metadata verified as version 99.98.97

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 65.31%. Comparing base (633b021) to head (72eead2).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #595   +/-   ##
=======================================
  Coverage   65.31%   65.31%           
=======================================
  Files          36       36           
  Lines       67969    67969           
  Branches     4904     4904           
=======================================
  Hits        44397    44397           
  Misses      23320    23320           
  Partials      252      252           

Flag	Coverage Δ
integration	64.34% <ø> (ø)
unit	65.03% <ø> (ø)

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