v2.6.0: Content backup/git versioning, plugin type system, docs update

New features:
- ContentBackup class with ZIP backup/restore and git versioning
- Admin backup & restore page (content-backup.twig) with git init/commit/log/restore
- Plugin type system: system (blue) vs content (green) with visual badges
- PluginAPIInterface + AdminPluginAPI for plugin architecture
- Essential plugin flag (cannot edit/deactivate/delete)

Improvements:
- Consolidated enabled_plugins config (removed plugins.enabled)
- Removed Analytics/Logging toggles from admin config page
- Fixed Dashboard plugin Twig comments rendered as text
- Updated 20 guide files (NL+EN): configuratie, plugins, plugin-development,
  core-classes, theme-json, layouts, scss-styling, admin-beheerder, nieuw-thema, architectuur
- Improved accessibility test script (grep -E, min/max checks)

Cleanup:
- Removed unused classes: ARIAComponents, AccessibilityManager, ContentSecurityPolicy, etc.
- Removed vendor packages: mustache/mustache, php-mqtt/client
- Removed old templates: logs.twig, statistics.twig (now plugins)
- Moved language files to language/ directory

Tests:
- Pentest: 30/30 passed, 0 vulnerabilities
- WCAG 2.1 AA: 25/25 passed, 100% compliance

AGENTS.md

@@ -18,15 +18,14 @@ codepress/
 │   │   ├── class/
 │   │   │   ├── CodePressCMS.php    # Hoofd CMS class
 │   │   │   ├── ThemeManager.php    # Thema-resolver + Twig render + SCSS compile
-│   │   │   ├── Logger.php          # Logging systeem
-│   │   │   └── SimpleTemplate.php  # Legacy Mustache-style engine (niet meer gebruikt)
+│   │   │   └── Logger.php          # Logging systeem
 │   │   ├── plugin/
 │   │   │   ├── PluginManager.php   # Plugin loader
 │   │   │   └── CMSAPI.php          # API voor plugins
 │   │   ├── config.php              # Config loader (leest config.json)
 │   │   └── index.php               # Bootstrap (autoloader, requires)
-│   ├── lang/                       # Taalbestanden (nl.php, en.php)
 │   └── router.php                  # PHP dev server router (serveert ook /themes/)
+├── language/                       # Taalbestanden (nl/, en/, de/ — elk met site.php + admin.php)
 ├── themes/                         # Dynamische thema's (volledig zelfstandig)
 │   ├── default/                    # Standaard thema
 │   │   ├── theme.json              # { title, default_layout, layout→.twig mapping, kleuren }
@@ -34,33 +33,24 @@ codepress/
 │   │   ├── full_content.twig       # Layout: volledige breedte
 │   │   ├── left_sidebar.twig       # Layout: sidebar links
 │   │   ├── right_sidebar.twig      # Layout: sidebar rechts
-│   │   ├── custom1.twig             # Layout: custom
+│   │   ├── custom1.twig            # Layout: custom
+│   │   ├── guide.twig              # Layout: handleiding
 │   │   ├── partials/               # header.twig, navigation.twig, footer.twig
-│   │   ├── css/theme.scss          # SCSS bron (runtime gecompileerd)
-│   │   └── js/theme.js             # Thema JavaScript
+│   │   ├── assets/scss/theme.scss  # SCSS bron (runtime gecompileerd)
+│   │   └── assets/js/              # app.js, bootstrap.bundle.min.js
 │   ├── demo/                       # Demo thema (zelfde structuur, andere look)
-│   └── test/                        # Test thema
 ├── admin/                          # Admin paneel
 │   ├── config/
 │   │   ├── app.php                # Admin app configuratie
-│   │   └── admin.json             # Gebruikers & security (file-based)
+│   │   ├── admin.json             # Gebruikers & security (file-based, gitignored)
+│   │   └── admin.json.example     # Voorbeeld met placeholder-wachtwoord
 │   ├── src/
 │   │   └── AdminAuth.php          # Authenticatie (sessies, bcrypt, CSRF, lockout)
-│   ├── templates/
-│   │   ├── login.php              # Login pagina
-│   │   ├── layout.php             # Admin layout met sidebar
-│   │   └── pages/
-│   │       ├── dashboard.php
-│   │       ├── content.php
-│   │       ├── content-edit.php
-│   │       ├── content-new.php
-│   │       ├── content-dir-form.php
-│   │       ├── config.php
-│   │       ├── plugins.php
-│   │       ├── plugin-config.php
-│   │       ├── theme.php
-│   │       └── users.php
-│   └── storage/logs/              # Admin logs
+│   ├── theme/default/views/        # Twig templates
+│   │   ├── login.twig             # Login pagina
+│   │   ├── layouts/admin.twig     # Admin layout met sidebar
+│   │   └── pages/                 # dashboard, content, content-edit, config, plugins, theme, users, statistics, logs, security, update, guide, media, etc.
+│   └── storage/logs/              # Admin logs (gedeeld met front-end)
 ├── cli/                            # CLI scripts & tests
 │   └── test/
 │       ├── accessibility.sh        # WCAG 2.1 AA test suite
@@ -69,7 +59,7 @@ codepress/
 │       └── pentest/                # Penetratietesten
 ├── plugins/                        # CMS plugins
 │   ├── HTMLBlock/
-│   └── MQTTTracker/
+│   └── Navigation/
 ├── public/                         # Web root
 │   ├── assets/css/js/
 │   ├── index.php                  # Website entry point
@@ -92,7 +82,7 @@ codepress/
   - Admin entry point + routing: `public/admin.php`
   - Admin authenticatie: `admin/src/AdminAuth.php`
 - **Content**: Stored in `content/`. Supports `.md` (Markdown), `.php` (Dynamic), `.html` (Static).
-- **Templating**: Twig templates in `themes/<naam>/`. `ThemeManager` rendert via Twig en compileert `css/theme.scss` runtime naar `public/themes/<naam>/theme.css`. Layout gekozen via frontmatter `layout:` key; onbekende layouts vallen terug op `default_layout` in `theme.json`.
+- **Templating**: Twig templates in `themes/<naam>/`. `ThemeManager` rendert via Twig en compileert `assets/scss/theme.scss` runtime naar `public/themes/<naam>/theme.css`. Layout gekozen via frontmatter `layout:` key; onbekende layouts vallen terug op `default_layout` in `theme.json`.
 - **Navigation**: Auto-generated from directory structure. Folders require an index file to be clickable in breadcrumbs.
 - **Security**: 
   - Always use `htmlspecialchars()` for outputting user/content data
@@ -104,9 +94,9 @@ codepress/
 ## Admin Console
 - **File-based**: Geen database. Gebruikers opgeslagen in `admin/config/admin.json`
 - **Routing**: Via `?route=` parameter in `public/admin.php`
-- **Routes**: `login`, `logout`, `dashboard`, `content`, `content-edit`, `content-new`, `content-delete`, `config`, `plugins`, `plugins-new`, `plugins-edit`, `plugins-config`, `plugins-toggle`, `plugins-delete`, `users`
+- **Routes**: `login`, `logout`, `dashboard`, `content`, `content-edit`, `content-new`, `content-delete`, `content-dir-create`, `content-dir-rename`, `content-dir-delete`, `content-move`, `config`, `plugins`, `plugins-new`, `plugins-edit`, `plugins-config`, `plugins-toggle`, `plugins-delete`, `theme`, `theme-new`, `users`, `security`, `statistics`, `logs`, `guide`, `media`, `update`
 - **Auth**: Session-based. `AdminAuth` class handelt login, logout, CSRF, brute-force lockout af
-- **Templates**: Pure PHP templates in `admin/templates/pages/`. Layout in `layout.php`
+- **Templates**: Twig templates in `admin/theme/default/views/`. Layout in `layouts/admin.twig`
 
 ## Important: Title vs File/Directory Name Logic
 - **CRITICAL**: When user asks for "title" corrections, they usually mean **FILE/DIRECTORY NAME WITHOUT LANGUAGE PREFIX AND EXTENSIONS**, not the HTML title from content!
@@ -121,5 +111,5 @@ codepress/
 ## Bekende aandachtspunten
 - LSP errors over "Undefined function" in PHP files zijn vals-positief (standaard PHP functies worden niet herkend door de LSP). Negeer deze.
 - Zie `TODO.md` voor alle openstaande verbeteringen en nieuwe features.
-- `vendor/` map bevat Composer dependencies (CommonMark, Twig, scssphp, Mustache). Niet handmatig wijzigen.
+- `vendor/` map bevat Composer dependencies (CommonMark, Twig, scssphp, GeoIP2). Niet handmatig wijzigen.
 - `admin/config/admin.json` bevat wachtwoord-hashes. Niet committen met echte productie-wachtwoorden.