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

admin/templates/layout.php

@@ -137,6 +137,9 @@
             case 'content-dir-rename':
                 require __DIR__ . '/pages/content-dir-form.php';
                 break;
+            case 'content-move':
+                require __DIR__ . '/pages/content-move-form.php';
+                break;
             case 'users':
                 require __DIR__ . '/pages/users.php';
                 break;