Media browser: recursive scan entire content/ tree, /-media/ URL prefix, editor change detection fix

- handleMediaList() now scans content/ recursively for all media files
- URLs use /-media/ prefix mapping directly to content/ (no special cases)
- index.php: added /-media/ route, kept /-assets/ for backward compat
- editor-toolbar.js: fixed editor.on('change') placement (was inside switchMode)
- content-edit.php and content-new.php: back-btn unsaved-changes detection
- Removed unused __editorCleanup global

cms/core/config.php

@@ -17,6 +17,17 @@ if (file_exists($configJsonPath)) {
             $config['templates_dir'] = $projectRoot . $config['templates_dir'];
         }
 
+        // Load active theme
+        $activeTheme = $config['active_theme'] ?? 'default';
+        $themeDir = __DIR__ . '/../../themes/' . $activeTheme;
+        $themeFile = $themeDir . '/theme.json';
+        if (file_exists($themeFile)) {
+            $themeConfig = json_decode(file_get_contents($themeFile), true);
+            $config['theme'] = $themeConfig;
+        } else {
+            $config['theme'] = [];
+        }
+
         return $config;
     }
 }