feat(auth): keep remember tokens on session timeout

- add timeout-specific logout path without remember-token revocation

- reset session timers after remember-me auto login

- compact session policy wording in admin settings (DE/EN)

- extend auth tests for timeout/manual logout behavior

web/index.php

@@ -79,7 +79,7 @@ if (!empty($_SESSION['user']['id'])) {
     $isAbsolute = ($now - $sessionStartedAt) > $absoluteTimeoutSeconds;
 
     if ($isIdle || $isAbsolute) {
-        $authService->logout();
+        $authService->logoutDueToSessionTimeout();
         Flash::error(t('Your session has expired. Please log in again.'), 'login', 'session_timeout');
         Router::redirect('login');
     }