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/composer.json

@@ -0,0 +1,38 @@
+{
+    "name": "symfony/polyfill-mbstring",
+    "type": "library",
+    "description": "Symfony polyfill for the Mbstring extension",
+    "keywords": ["polyfill", "shim", "compatibility", "portable", "mbstring"],
+    "homepage": "https://symfony.com",
+    "license": "MIT",
+    "authors": [
+        {
+            "name": "Nicolas Grekas",
+            "email": "p@tchwork.com"
+        },
+        {
+            "name": "Symfony Community",
+            "homepage": "https://symfony.com/contributors"
+        }
+    ],
+    "require": {
+        "php": ">=7.2"
+    },
+    "provide": {
+        "ext-mbstring": "*"
+    },
+    "autoload": {
+        "psr-4": { "Symfony\\Polyfill\\Mbstring\\": "" },
+        "files": [ "bootstrap.php" ]
+    },
+    "suggest": {
+        "ext-mbstring": "For best performance"
+    },
+    "minimum-stability": "dev",
+    "extra": {
+        "thanks": {
+            "name": "symfony/polyfill",
+            "url": "https://github.com/symfony/polyfill"
+        }
+    }
+}