CMS 2.0 - Theme engine, logging, admin improvements

Major changes:
- New ThemeManager with Twig templating and SCSS compilation
- Dynamic themes system (themes/default, themes/demo)
- LogManager with SQLite storage and syslog forwarding
- RequestLogger with static helper methods
- Admin UI overhaul (Bootstrap 5, dark mode)
- Admin config page with logging and theme settings
- Admin logs page with filters and search
- Removed legacy Mustache templates
- Removed test plugin and theme
- Composer dependencies: Twig, scssphp, CommonMark, MaxMind GeoIP

vendor/symfony/polyfill-mbstring/README.md

@@ -0,0 +1,13 @@
+Symfony Polyfill / Mbstring
+===========================
+
+This component provides a partial, native PHP implementation for the
+[Mbstring](https://php.net/mbstring) extension.
+
+More information can be found in the
+[main Polyfill README](https://github.com/symfony/polyfill/blob/main/README.md).
+
+License
+=======
+
+This library is released under the [MIT license](LICENSE).