security: harden static site (headers, exposed-file cleanup, privacy)

Proactive security & health pass. No live/exploitable vulnerabilities were
found; these changes remove information-disclosure surfaces and add
standard hardening.

- Remove publicly-downloadable 1.1 MB full source dump (code_export.txt)
  and stray empty l.php; add code_export.txt to .gitignore.
- Exclude dev files/folders (*.sh, *.py, docs/, templates/, tools/,
  README.md) from the rsync deploy so they never reach the live server.
- .htaccess: add X-Frame-Options, Referrer-Policy, Permissions-Policy,
  and a report-only Content-Security-Policy; add defense-in-depth deny
  block for dev/VCS files (robots.txt & sitemap.xml left served).
- .htaccess: fix root redirect to canonical msosorg.com + /en/.
- Swap 4 project-page YouTube embeds to youtube-nocookie.com so no
  Google cookies are set before consent (GDPR).
- Add rel="noopener" to 30 team social links on the About Us pages.
- Harden esc() in my-route.js to also escape single quotes.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.gitea/workflows/deploy.yml

@@ -23,6 +23,13 @@ jobs:
             --exclude=".git/" \
             --exclude=".gitea/" \
             --exclude=".gitignore" \
+            --exclude="README.md" \
+            --exclude="*.sh" \
+            --exclude="*.py" \
+            --exclude="code_export.txt" \
+            --exclude="docs/" \
+            --exclude="templates/" \
+            --exclude="tools/" \
             -e "ssh -p ${{ secrets.SSH_PORT }} -i ~/.ssh/id_rsa -o StrictHostKeyChecking=no" \
             ./ \
             ${{ secrets.SSH_USER }}@${{ secrets.SSH_HOST }}:${{ secrets.TARGET_DIR }}