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/theme-developer.md

@@ -3,7 +3,7 @@
 The theme developer guide contains the following topics:
 
 - **Theme structure** - Folder structure of a theme
-- **theme.json** - Theme configuration
+- **theme.json** - Configuration of a theme
 - **Twig templates** - Twig syntax, variables and blocks
 - **SCSS styling** - Compiling and writing SCSS
 - **Layouts** - Defining and using layouts