Update all guides (NL + EN) for CodePress 2.5.2 features

- Admin guide: RBAC roles, role-based dashboard, plugin types (content/system)
- CodePress developer guide: plugin types, admin plugin API, SCSS compilation, asset serving
- Theme developer guide: SCSS sole CSS source, css_compiled read-only, guide layout
- Content manager guide: layout selection from theme.json, plugin order in frontmatter
- Both NL and EN updated with identical structure
- 35 files updated

guide/en/codepress-developer/plugin-development.md

@@ -1,43 +1,144 @@
 # Plugin Development
 
+## Plugin types
+
+CodePress has two kinds of plugins, determined by the `type` field in `plugin.json`:
+
+- **Content plugins** (`type: "content"`) — Appear in the sidebar and in the plugin selection on content-edit pages. Provide sidebar content via `getSidebarContent()`.
+- **System plugins** (`type: "system"`) — Are loaded by PluginManager but do NOT appear in the sidebar. Provide functionality via admin menu, routes and the CMSAPI.
+
+When no `type` field is present, `content` is assumed.
+
 ## Plugin structure
 
 ```
 plugins/MyPlugin/
-├── plugin.json         # Plugin metadata
-├── plugin.php          # Plugin code
-└── config.json         # Optional configuration
+├── MyPlugin.php        # Plugin code (NOT plugin.php)
+├── plugin.json           # Metadata with type field
+├── config.json           # Optional configuration
+└── assets/
+    ├── scss/myplugin.scss  # SCSS source (optional)
+    └── css/myplugin.css    # CSS (manually maintained)
 ```
 
+Plugin files are named `<PluginName>.php` (e.g. `Navigation.php`, `HTMLBlock.php`). `PluginManager` loads `$pluginDir . '/' . $pluginName . '.php'`.
+
 ## plugin.json
 
 ```json
 {
-  "name": "My Plugin",
-  "version": "1.0.0",
-  "author": "Your Name",
-  "description": "Description"
+    "name": "My Plugin",
+    "version": "1.0.0",
+    "author": "Your Name",
+    "description": "Description",
+    "type": "content"
 }
 ```
 
-## plugin.php example
+- `name` — Display name
+- `type` — `"content"` or `"system"` (default: `content`)
+
+## Content plugin example
 
 ```php
 <?php
 /**
- * Plugin: MyPlugin
+ * Plugin: MyPlugin (content)
  */
+class MyPlugin
+{
+    public function getConfig(): array
+    {
+        return [
+            'title' => 'My Plugin',
+            'type' => 'content',
+        ];
+    }
 
-echo '<div class="my-plugin">Hello World</div>';
+    public function getSidebarContent(): string
+    {
+        return '<p>Hello World</p>';
+    }
+}
 ```
 
+## System plugin example
+
+```php
+<?php
+/**
+ * Plugin: MySystem (system)
+ */
+class MySystem
+{
+    public function getConfig(): array
+    {
+        return [
+            'title' => 'My System',
+            'type' => 'system',
+        ];
+    }
+
+    public function getAdminMenu(): array
+    {
+        return [
+            ['label' => 'My System', 'route' => 'my-system', 'icon' => 'bi-gear'],
+        ];
+    }
+
+    public function getAdminRoutes(): array
+    {
+        return ['my-system'];
+    }
+
+    public function handleAdminRoute(string $route): void
+    {
+        echo '<h1>My System page</h1>';
+    }
+}
+```
+
+System plugins are shown in the admin sidebar via `PluginManager::getAdminMenuItems()` and handled via `PluginManager::handleAdminRoute()`.
+
 ## Using CMSAPI
 
 ```php
 <?php
-require_once '../../cms/core/class/PluginManager.php';
-
 $api = PluginManager::getAPI();
 $config = $api->getConfig();
-$content = $api->getContent();
-```
+$page = $api->getPage($path);
+```
+
+`setAPI()` is called automatically by `PluginManager` if the plugin has the method.
+
+## Plugin CSS
+
+- Plugin CSS in `assets/css/` is manually maintained (SCSS compilation for plugins is not yet automatic)
+- Plugin CSS is automatically loaded after theme CSS (in `base.twig`), so themes can override plugin styling
+- Plugin assets are served via `cms/router.php` at URL `/plugins/<Name>/assets/...`
+- Implement `getCssUrl()` in the plugin class to return the CSS URL
+
+```php
+public function getCssUrl(): string
+{
+    return '/plugins/MyPlugin/assets/css/myplugin.css';
+}
+```
+
+## Hooks and filters
+
+PluginManager auto-registers these methods as hooks/filters:
+
+- **Hooks**: `onPageLoad`, `onBeforeRender`, `onAfterRender`, `onSearch`, `onMenuBuild`
+- **Filters**: `onContentFilter`, `onTitleFilter`, `onMenuFilter`
+
+```php
+public function onPageLoad($page) { /* ... */ }
+public function onContentFilter($content) { return $content; }
+```
+
+## Essential plugins
+
+Essential plugins are defined in `getProtectedPlugins()` in `public/admin.php`. Current essential plugin: **Navigation**.
+
+These plugins cannot be deactivated, edited or deleted. Always add the `isProtectedPlugin()` check to new plugin handlers.