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/psr/http-message/README.md

@@ -0,0 +1,16 @@
+PSR Http Message
+================
+
+This repository holds all interfaces/classes/traits related to
+[PSR-7](http://www.php-fig.org/psr/psr-7/).
+
+Note that this is not a HTTP message implementation of its own. It is merely an
+interface that describes a HTTP message. See the specification for more details.
+
+Usage
+-----
+
+Before reading the usage guide we recommend reading the PSR-7 interfaces method list:
+
+* [`PSR-7 Interfaces Method List`](docs/PSR7-Interfaces.md)
+* [`PSR-7 Usage Guide`](docs/PSR7-Usage.md)