docs: add timestamp annotations to all documentation headings

[joshuaquek]

Add standardized timestamp annotations to all section/subsection headings in docs folder and README.md using the format:

[sonar-review-alpha]

Summary

This PR standardizes timestamp annotations across 26 documentation files and README.md. The format changes from informal comments like <!-- Last updated: 2026-03-25 --> to a structured format: <!-- <subsection-updated last-updated="2026-05-07T02:15:00Z" updated-by="Claude" /> -->. The annotations are added to section and subsection headings throughout the documentation, enabling machine-readable tracking of last-update times and author attribution.

Scope: 1024 insertions, 495 deletions across all docs files and main README.

What reviewers should know

Critical issue to verify before merging: HTML comment tags are inconsistently closed. Many lines end with just /> without the closing -->, which breaks the HTML comment syntax. For example:

• Line 3 of Audit & Error Events Logging Strategy.md: ends with /> (missing -->)
• Other occurrences where the closing tag is properly formed: <subsection-updated ... /> -->

One instance found where this causes actual text corruption (line ~395 in the audit strategy file where the comment tag merges with the next line content).

Reviewer checklist:

1. Verify all <subsection-updated tags properly close with /> followed by space and -->
2. Check that no content got merged into comment tags during the automated annotation process
3. Validate that all major headings received annotations (##, ###, etc.)
4. Confirm timestamp format is consistent (ISO 8601 with Z timezone) across all files

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