chore: bump version to v2026.4.313 and add dropdown scroll}
- Bump version from v2026.4.312 to v2026.4.313 across docs and package.json - Add scrollable dropdown styles for theme and language navigation menus - Apply p3x-gitlist-dropdown-scroll class with max-height and dark/light color-scheme support - Update CSS cache-busting hash in themes.js and package.json - Add v2026.4.313 changelog entry