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/admin-beheerder/content-beheer.md

@@ -2,16 +2,45 @@
 
 ## Managing files
 
-- **Upload** - Upload media files
-- **New folder** - Create folder structure
-- **New file** - Create a page
-- **Edit** - Modify existing content
-- **Rename** - Change file names
-- **Move** - Move content
-- **Delete** - Remove content
+- **New folder** — Create folder structure
+- **New file** — Create a page (`.md`, `.php`, `.html`)
+- **Edit** — Modify existing content in the CodeMirror editor
+- **Rename** — Change file or folder names
+- **Move** — Move content to another folder
+- **Delete** — Remove content
+- **Rename folder** — Change a folder name
 
-## Editor
+## Editor (content-edit)
 
-- CodeMirror with syntax highlighting
-- Toolbar for Markdown formatting
-- Shortcuts: Ctrl+S (save), Ctrl+N (new)
+- **CodeMirror** with syntax highlighting (Markdown, PHP, HTML)
+- **Toolbar** for quickly inserting Markdown
+- **Shortcuts**: Ctrl+S (save), Ctrl+N (new)
+
+## Layout selection
+
+On the content-edit page you can choose the layout from the layouts defined in `theme.json` (template mapping). The selected layout is stored in the frontmatter `layout:` key.
+
+## Plugins on pages
+
+- Content plugins (from `plugin.json` with `type: "content"`) appear in the plugin selection
+- Choose which plugins appear in the sidebar
+- **Order is adjustable** with up/down buttons
+- The plugin order is stored in the frontmatter `plugins:` key
+- Plugins are **hidden** when the chosen layout has no sidebar (e.g. `full_content`)
+
+## Frontmatter
+
+The editor updates the frontmatter live when layout or plugin selection changes:
+
+```markdown
+---
+layout: left_sidebar
+plugins:
+  - HTMLBlock
+  - Navigation
+---
+
+# Page title
+
+Content...
+```