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

cli/test/functional/function-test.md

@@ -333,7 +333,7 @@ This document outlines comprehensive functional tests for CodePress CMS to verif
 
 **Steps:**
 1. Try accessing `/content/` directly
-2. Try accessing `/engine/` files
+2. Try accessing `/cms/` files
 3. Try accessing `config.php`
 4. Try accessing `/vendor/`