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.md

@@ -2,13 +2,20 @@
 
 The CodePress developer guide contains the following topics:
 
-- **Architecture** - CMS architecture and folder structure
-- **Core classes** - CodePressCMS, ThemeManager, PluginManager
-- **Plugin development** - Developing plugins
-- **Routing** - Frontend and admin routing
-- **Security** - XSS, CSRF, path traversal
-- **Testing** - Penetration, accessibility and functional tests
-- **Debugging** - Logging and cache
-- **Performance** - OPcache and SCSS caching
+- **Architecture** — CMS architecture and folder structure
+- **Core classes** — CodePressCMS, ThemeManager, PluginManager, AdminAuth
+- **Plugin development** — Plugin types (content/system), structure, API
+- **Routing** — Frontend, admin and plugin admin routing
+- **Security** — XSS, CSRF, path traversal, RBAC
+- **Testing** — Penetration, accessibility and functional tests
+- **Debugging** — Logging and cache
+- **Performance** — OPcache and SCSS caching
+
+Important concepts in CodePress 2.5.2:
+
+- **Plugin types** — Content plugins (sidebar) and system plugins (admin menu, routes, API)
+- **Admin plugin API** — System plugins can register admin menu items and routes
+- **SCSS compilation** — `ThemeManager` compiles SCSS to `css_compiled/` via scssphp (read-only)
+- **Asset serving** — `public/asset.php` serves themes/, admin/assets/ and plugins/ on Apache (instead of PHP dev router)
 
 Select a topic from the navigation on the left.