Dispatcher: fix trigger404 using nonexistent ViewErrorPage class

Use the existing errorPage() helper, consistent with trigger400 and
trigger403.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

models/Dispatcher.php

@@ -90,7 +90,7 @@ class Dispatcher
 	private static function trigger404()
 	{
 		http_response_code(404);
-		$page = new ViewErrorPage('Page not found!');
-		$page->showContent();
+		self::errorPage('Page not found!', 'The page you requested could not be found.');
+		exit;
 	}
 }