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/plugin/PluginManager.php

@@ -16,7 +16,6 @@ class PluginManager
     {
         $this->api = $api;
         
-        // Inject API into all plugins that have setAPI method
         foreach ($this->plugins as $plugin) {
             if (method_exists($plugin, 'setAPI')) {
                 $plugin->setAPI($api);
@@ -43,7 +42,6 @@ class PluginManager
                 if (class_exists($className)) {
                     $this->plugins[$pluginName] = new $className();
                     
-                    // Inject API if already available
                     if ($this->api && method_exists($this->plugins[$pluginName], 'setAPI')) {
                         $this->plugins[$pluginName]->setAPI($this->api);
                     }
@@ -62,14 +60,49 @@ class PluginManager
         return $this->plugins;
     }
 
-    public function getSidebarContent(): string
+    public function isPluginViewable(object $plugin): bool
+    {
+        if (method_exists($plugin, 'getConfig')) {
+            $config = $plugin->getConfig();
+            return !isset($config['viewable']) || $config['viewable'] !== false;
+        }
+        return true;
+    }
+
+    public function getSidebarContent(?array $allowedPlugins = null): string
     {
         $sidebarContent = '';
         
-        foreach ($this->plugins as $plugin) {
-            if (method_exists($plugin, 'getSidebarContent')) {
-                $sidebarContent .= $plugin->getSidebarContent();
+        foreach ($this->plugins as $pluginName => $plugin) {
+            if (!$this->isPluginViewable($plugin) || !method_exists($plugin, 'getSidebarContent')) {
+                continue;
             }
+            
+            // Filter by allowed plugins for this page
+            if ($allowedPlugins !== null && !in_array($pluginName, $allowedPlugins, true)) {
+                continue;
+            }
+            
+            $content = $plugin->getSidebarContent();
+            if (trim($content) === '') {
+                continue;
+            }
+            
+            $title = 'Plugin';
+            if (method_exists($plugin, 'getConfig')) {
+                $config = $plugin->getConfig();
+                $title = $config['title'] ?? 'Plugin';
+            }
+            
+            $sidebarContent .= '
+                <div class="card mb-3">
+                    <div class="card-header">
+                        <h5 class="mb-0">' . htmlspecialchars($title) . '</h5>
+                    </div>
+                    <div class="card-body">
+                        ' . $content . '
+                    </div>
+                </div>';
         }
         
         return $sidebarContent;