feat: restructure settings menu + add automation/agents to topbar

TopBar:
- Add Automation and Agenten to user dropdown menu

Settings restructure:
- Stammdaten: Firmendaten, Adressen (CRUD), Konten (CRUD), Sonstige Daten
- Nutzerverwaltung: Benutzer, Rollen, Gruppen as tabs
- System: Menü, Theme, Plugins as tabs
- Reduce nav items from 15+ to 8
- Add end prop to all settings NavLinks

frontend/src/routes/index.tsx

@@ -37,6 +37,8 @@ const ProactiveAISettings = React.lazy(() => import('@/pages/ProactiveAISettings
 const SettingsThemePage = React.lazy(() => import('@/pages/SettingsTheme').then(m => ({ default: m.SettingsThemePage })));
 const SettingsMcpPage = React.lazy(() => import('@/pages/SettingsMcp').then(m => ({ default: m.SettingsMcpPage })));
 const SettingsMenuOrderPage = React.lazy(() => import('@/pages/SettingsMenuOrder').then(m => ({ default: m.SettingsMenuOrderPage })));
+const SettingsStammdatenPage = React.lazy(() => import('@/pages/SettingsStammdaten').then(m => ({ default: m.SettingsStammdatenPage })));
+const SettingsUserManagementPage = React.lazy(() => import('@/pages/SettingsUserManagement').then(m => ({ default: m.SettingsUserManagementPage })));
 const AutomationDashboardPage = React.lazy(() => import('@/pages/AutomationDashboard').then(m => ({ default: m.AutomationDashboardPage })));
 const AgentDashboardPage = React.lazy(() => import('@/pages/AgentDashboard').then(m => ({ default: m.AgentDashboardPage })));
 const AutomationSettingsPage = React.lazy(() => import('@/pages/AutomationSettings').then(m => ({ default: m.AutomationSettingsPage })));
@@ -99,6 +101,8 @@ const router = createBrowserRouter([
         path: '/settings',
         element: withSuspense(<SettingsPage />),
         children: [
+          { path: 'stammdaten', element: withSuspense(<SettingsStammdatenPage />) },
+          { path: 'user-management', element: withSuspense(<SettingsUserManagementPage />) },
           { path: 'roles', element: withSuspense(<SettingsRolesPage />) },
           { path: 'users', element: withSuspense(<SettingsUsersPage />) },
           { path: 'groups', element: withSuspense(<SettingsGroupsPage />) },