Improve course lab setup safety

[jules-tth]

Scope

• Expand docs/course/lab-setup.md with practical lab goals for safe Linux learning.
• Add recommended baselines for local VMs, cloud VMs, and containers.
• Add preflight evidence commands, snapshot/rollback naming guidance, and cleanup checks.

Verification

• python -m pip install -r requirements.txt could not run because python is not on PATH.
• python3 -m pip install -r requirements.txt passed.
• python3 -m mkdocs build --strict passed.
• make build passed.
• git diff --check passed.
• find docs -type f -name "*.md" -size 0 -print returned no files.

Duplicate prevention

• Checked open PRs from jules-tth; existing lesson PRs cover Chapter 01 through Chapter 31 plus docs/course/syllabus.md and docs/course/glossary.md.
• Final target-file query returned no open PR touching docs/course/lab-setup.md.

[jules-tth]

Reviewer assignment to bdorlus failed during PR creation: GraphQL: jules-tth does not have the correct permissions to execute RequestReviewsByLogin (requestReviewsByLogin)