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

cms/router.php

@@ -30,6 +30,26 @@ if (is_file($filePath)) {
     return true;
 }
 
+// Serve theme assets from the themes/ directory (e.g. /themes/default/js/theme.js)
+if (preg_match('#^/themes/([^/]+)/(.+)$#', $path, $m)) {
+    $themeName = $m[1];
+    $themeRel = $m[2];
+    $themesDir = __DIR__ . '/../themes';
+    $themeFile = $themesDir . '/' . $themeName . '/' . $themeRel;
+    $realThemes = realpath($themesDir);
+    $realFile = realpath($themeFile);
+    if ($realFile && $realThemes && strpos($realFile, $realThemes) === 0 && is_file($realFile)) {
+        $ext = strtolower(pathinfo($realFile, PATHINFO_EXTENSION));
+        if (isset($mimeTypes[$ext])) {
+            header('Content-Type: ' . $mimeTypes[$ext]);
+        }
+        readfile($realFile);
+        return true;
+    }
+    http_response_code(404);
+    return true;
+}
+
 // Admin routes: /admin/login → admin.php?route=login
 if (preg_match('#^/admin(?:/(.+))?$#', $path, $m)) {
     $_GET['route'] = $m[1] ?? 'dashboard';