add missing namespaces/fix wrong class-names

src/App/Router.php

@@ -8,6 +8,7 @@ use FastRoute\Dispatcher;
 use FastRoute\RouteCollector;
 use FastRoute\RouteParser\Std;
 use Friendica\Core\Hook;
+use Friendica\DI;
 use Friendica\Network\HTTPException;
 
 /**