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

admin/templates/pages/content-new.php

@@ -28,11 +28,17 @@
                 <div class="col-md-6">
                     <label for="layout" class="form-label">Sjabloon / Layout</label>
                     <select class="form-select" id="layout" name="layout">
+                        <?php if (empty($themeLayouts)): ?>
                         <option value="sidebar-content">Sidebar + Inhoud (standaard)</option>
                         <option value="content">Alleen inhoud (full-width)</option>
                         <option value="sidebar">Alleen sidebar (full-width)</option>
                         <option value="content-sidebar">Inhoud links + sidebar rechts</option>
                         <option value="content-sidebar-reverse">Inhoud rechts + sidebar links</option>
+                        <?php else: ?>
+                        <?php foreach ($themeLayouts as $key => $file): ?>
+                        <option value="<?= htmlspecialchars($key) ?>"><?= htmlspecialchars(ucfirst(str_replace('_', ' ', $key))) ?></option>
+                        <?php endforeach; ?>
+                        <?php endif; ?>
                     </select>
                 </div>
                 <?php if (!empty($availablePlugins)): ?>