[Maintenance] Pin Python dependencies to current 3.10-compatible versions

[terrancedejesus]

Summary

• Pin direct Poetry dependencies to current versions that still support Python 3.10 (CI and ReadTheDocs).
• Add poetry.lock so installs are reproducible.
• Remove the unused deprecated [tool.poetry.dev-dependencies] section.

This supersedes the stale Renovate PRs that bumped 2023 hashes one package at a time (#80, #82–#89).

Pins chosen for Python 3.10 compatibility:

• google-auth 2.56.3, google-auth-oauthlib 1.4.0, google-auth-httplib2 0.4.1, google-api-python-client 2.198.0
• PyYAML 6.0.3, requests 2.34.2, semver 3.0.4, tabulate 0.10.0
• pandas 2.3.3 (optional; 3.x requires 3.11+)
• selenium 4.47.0
• sphinx 8.1.3 (8.2+ requires 3.11; 9.x requires 3.12)
• sphinx-rtd-theme 3.1.0
• pytest 8.4.2

docs/requirements.txt is left for a follow-up PR so this review stays mid-size.

Test plan

• poetry install
• poetry run pytest tests/ -v — 36 passed
• CI pytest job on Python 3.10