Improve Chapter 31 compliance lesson

[jules-tth]

Summary

• Rewrites the Chapter 31.8 compliance/regulations/standards lesson as a practical Linux operations guide.
• Covers regulations vs standards vs policies vs controls, common frameworks, Linux control evidence, access/patch/log/network/data/backup/change-management practices, exceptions, common mistakes, and a reversible lab.

Duplicate prevention

• Verified PR Improve Chapter 31 SLA lesson #289 is the canonical Chapter 31 SLA slice.
• Final target-file overlap check returned no open PR touching docs/lessons/31_methodology_policy_and_politics/31.8_compliance-_regulations_and_standards.md immediately before PR creation.

Verification

• python3 -m mkdocs build --strict
• git diff --check
• make build