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

admin/src/AdminAuth.php

@@ -16,7 +16,7 @@ class AdminAuth
      */
     public const ROLE_PERMISSIONS = [
         'admin' => ['*'],
-        'content-manager' => ['dashboard', 'content', 'content-edit', 'content-new', 'content-delete', 'content-dir-create', 'content-dir-rename', 'content-dir-delete', 'content-move', 'guide', 'logout'],
+        'content-manager' => ['dashboard', 'content', 'content-edit', 'content-new', 'content-delete', 'content-dir-create', 'content-dir-rename', 'content-dir-delete', 'content-move', 'content-backup', 'content-restore', 'content-git-init', 'content-git-commit', 'content-git-restore', 'guide', 'logout'],
         'bi-manager' => ['dashboard', 'statistics', 'logs', 'guide', 'logout'],
         'site-admin' => ['dashboard', 'theme', 'theme-new', 'plugins', 'plugins-new', 'plugins-edit', 'plugins-config', 'plugins-toggle', 'plugins-delete', 'statistics', 'logs', 'update', 'guide', 'logout'],
     ];
@@ -28,7 +28,7 @@ class AdminAuth
         'admin' => 'Admin',
         'content-manager' => 'Content Beheerder',
         'bi-manager' => 'BI Beheerder',
-        'site-admin' => ' Site Admin',
+        'site-admin' => 'Site Admin',
     ];
 
     public function __construct(array $appConfig)
@@ -170,10 +170,19 @@ class AdminAuth
         if (!$this->isAuthenticated()) {
             return null;
         }
-        return [
-            'username' => $_SESSION['admin_user'],
+        $username = $_SESSION['admin_user'];
+        $userData = [
+            'username' => $username,
             'role' => $_SESSION['admin_role'] ?? 'admin'
         ];
+        // Enrich with profile fields from admin.json
+        $userEntry = $this->findUser($username);
+        if ($userEntry) {
+            $userData['email'] = $userEntry['email'] ?? '';
+            $userData['author_name'] = $userEntry['author_name'] ?? '';
+            $userData['author_email'] = $userEntry['author_email'] ?? '';
+        }
+        return $userData;
     }
 
     /**
@@ -244,13 +253,16 @@ class AdminAuth
                 'username' => $u['username'],
                 'role' => $role,
                 'role_label' => self::getRoleLabel($role),
-                'created' => $u['created'] ?? ''
+                'created' => $u['created'] ?? '',
+                'email' => $u['email'] ?? '',
+                'author_name' => $u['author_name'] ?? '',
+                'author_email' => $u['author_email'] ?? '',
             ];
         }
         return $users;
     }
 
-    public function addUser(string $username, string $password, string $role = 'admin'): array
+    public function addUser(string $username, string $password, string $role = 'admin', string $email = '', string $authorName = '', string $authorEmail = ''): array
     {
         if ($this->findUser($username)) {
             return ['success' => false, 'message' => 'Gebruiker bestaat al.'];
@@ -266,6 +278,9 @@ class AdminAuth
             'username' => $username,
             'password_hash' => password_hash($password, PASSWORD_DEFAULT),
             'role' => $role,
+            'email' => $email,
+            'author_name' => $authorName,
+            'author_email' => $authorEmail,
             'created' => date('Y-m-d')
         ];
         $this->saveAdminConfig();
@@ -273,6 +288,24 @@ class AdminAuth
         return ['success' => true, 'message' => 'Gebruiker aangemaakt.'];
     }
 
+    /**
+     * Update the profile (email, author_name, author_email) of a user.
+     */
+    public function updateUserProfile(string $username, string $email = '', string $authorName = '', string $authorEmail = ''): array
+    {
+        foreach ($this->adminConfig['users'] as &$userEntry) {
+            if ($userEntry['username'] === $username) {
+                $userEntry['email'] = $email;
+                $userEntry['author_name'] = $authorName;
+                $userEntry['author_email'] = $authorEmail;
+                $this->saveAdminConfig();
+                $this->log('info', "Profiel bijgewerkt: {$username}");
+                return ['success' => true, 'message' => 'Profiel opgeslagen.'];
+            }
+        }
+        return ['success' => false, 'message' => 'Gebruiker niet gevonden.'];
+    }
+
     /**
      * Change the role of an existing user.
      */