Implement personal section in navigation: Add a new 'personal' menu item with sub-items for language learning and calendar. Update localization files for English and German to include translations for the new section. Integrate personal routes into the router configuration for navigation.

frontend/src/router/personalRoutes.js

@@ -0,0 +1,12 @@
+const CalendarView = () => import('../views/personal/CalendarView.vue');
+
+const personalRoutes = [
+    {
+        path: '/personal/calendar',
+        name: 'Calendar',
+        component: CalendarView,
+        meta: { requiresAuth: true }
+    }
+];
+
+export default personalRoutes;