feat: add auto language detection and fix light mode styling}
- Add "Auto" option to language dropdown that detects language from browser Accept-Language header with server-side parsing in PHP - Remove p3x-gitlist-language cookie when "Auto" is selected instead of storing a value, defaulting to auto-detection on next visit - Fix markdown tables not styled in rendered markdown views by extending Bootstrap .table, .table-striped, and .table-bordered - Fix hljs inline code background invisible in light themes by adding theme-aware background colors for .p3x-gitlist-light/dark classes - Update navigation template with Auto option, divider, and active state logic for both auto and manual language selections - Bump version to v2026.4.329 and update changelog - Regenerate CSS assets with new hash postfix