feat: redesign blame view with hljs syntax highlighting and porcelain parsing}
- Rewrite blame PHP backend to use `git blame --porcelain` for richer metadata (author, email, timestamp, summary) - Add hljs-based syntax highlighting to blame view with language detection by file extension - Extract shared hljs-loader module from marked.js to deduplicate highlight.js registration - Move highlight.js theme imports (github/github-dark) from _markdown.scss to _blame.scss for shared use - Redesign blame twig template to use flexbox layout with commit header tooltips showing summary - Simplify blame SCSS: remove old blame-container/row/hash/line-num classes, add new flex-based layout - Restrict nginx PHP handler to only index.php for security hardening - Bump version to v2026.4.309 with changelog entry - Update CSS cache-bust hash across all theme references