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

themes/demo/js/theme.js

@@ -0,0 +1,21 @@
+// CodePress default theme JavaScript
+// Loaded after the global app.js on every page.
+
+(function () {
+    'use strict';
+
+    // Sidebar toggle (used by the breadcrumb toggle button)
+    function toggleSidebar() {
+        var sidebar = document.getElementById('site-sidebar');
+        if (!sidebar) return;
+        sidebar.classList.toggle('sidebar-hidden');
+        var btn = document.querySelector('.sidebar-toggle-btn');
+        if (btn) {
+            var hidden = sidebar.classList.contains('sidebar-hidden');
+            btn.setAttribute('aria-expanded', hidden ? 'false' : 'true');
+        }
+    }
+
+    // Expose for inline onclick handlers
+    window.toggleSidebar = toggleSidebar;
+})();