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/content-beheerder/content-structuur.md

@@ -4,28 +4,48 @@ Content is stored in the `content/` folder without a database.
 
 ## Supported file formats
 
-- `.md` - Markdown (recommended)
-- `.php` - Dynamic PHP pages
-- `.html` - Static HTML pages
+- `.md` — Markdown (recommended)
+- `.php` — Dynamic PHP pages
+- `.html` — Static HTML pages
 
 ## File name conventions
 
 ```
-en.page-name.md     # English page
-nl.pagina-naam.md   # Dutch page
+nl.pagina-naam.md     # Dutch page
+en.page-name.md       # English page
+nl.folder/            # Dutch folder (requires an index file to be clickable)
 ```
 
+The language prefix is dynamically removed based on available languages via `getAvailableLanguages()`.
+
 ## Frontmatter
 
 Markdown files can contain frontmatter metadata:
 
 ```markdown
 ---
-layout: full_content
-plugins: HTMLBlock
+layout: left_sidebar
+plugins:
+  - HTMLBlock
+  - Navigation
 ---
 
 # Page title
 
 Content...
-```
+```
+
+## Frontmatter fields
+
+- `layout` — Layout name (must exist in the `theme.json` template mapping; fallback to `config.default_template`)
+- `plugins` — List of content plugins that appear in the sidebar
+
+### plugins field
+
+The `plugins` field determines:
+- **Which plugins** appear in the sidebar (only content plugins, not system plugins)
+- **The order** of the plugins in the sidebar (top to bottom)
+
+The order in the frontmatter is the order in which the plugins are shown. In the admin content-edit page you can adjust the order with up/down buttons; the frontmatter is updated live.
+
+Plugins are not shown when the chosen layout has no sidebar (e.g. `full_content`).