Make Produkte a flat nav item, remove Produkte navigation group

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

app/Providers/Filament/UserPanelProvider.php

@@ -39,7 +39,6 @@ class UserPanelProvider extends PanelProvider
             ->favicon(url:'../images/favicon.png')
 
             ->navigationGroups([
-                NavigationGroup::make('Produkte'),
                 NavigationGroup::make('Lager'),
                 NavigationGroup::make('Waren Ein/Ausgang'),
                 NavigationGroup::make('Ressourcen'),