Fix RTD build: mock remaining runtime dependencies

[JE-Chen]

Summary

RTD only installs docs/requirements.txt (sphinx + theme + mermaid), so any
top-level project dependency not listed in autodoc_mock_imports aborts the
autosummary import sweep with ModuleNotFoundError. Reproduced in a clean
local venv that mirrors RTD's setup (no selenium / webdriver_manager / requests
/ dotenv / defusedxml installed).

Added the missing four mocks to docs/source/conf.py:

• webdriver_manager (the actual culprit reported in the latest RTD log)
• requests
• dotenv
• defusedxml

After the change sphinx-build -W --keep-going succeeds in the selenium-less
venv with zero warnings.

Test plan

• RTD build green (latest + stable)
• cd docs && python -m sphinx -b html -W --keep-going source build/html clean in a venv that lacks the project deps

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codacy-production]

Up to standards ✅

🟢 Issues 0 issues

Results:
0 new issues

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