feat(pages): adapt defacement mirror for GitHub Pages deployment

- Add .nojekyll to prevent Jekyll ignoring _-prefixed directories
- Add .gitattributes with * -text to preserve line endings
- Replace 18 valid symlinks with file copies
- Add attrition.css and footer images from live site
- Replace SSI includes in index.html and remove-request-new-index.html
- Rewrite absolute href paths to attrition.org URLs or relative paths
- Update GitHub Actions workflow to deploy entire mirror/ directory
- Remove broken symlinks before tar in workflow to prevent upload failure

Author: mauvehed