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/views/personal/CalendarView.vue

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+<template>
+    <div class="calendar-view">
+        <h2>{{ $t('personal.calendar.title') }}</h2>
+        
+        <div class="coming-soon">
+            <img src="/images/icons/coming-soon.png" alt="Coming Soon" class="coming-soon-icon" />
+            <p>{{ $t('personal.calendar.comingSoon') }}</p>
+        </div>
+    </div>
+</template>
+
+<script>
+export default {
+    name: 'CalendarView',
+};
+</script>
+
+<style scoped lang="scss">
+.calendar-view {
+    padding: 20px;
+}
+
+h2 {
+    margin-bottom: 20px;
+    color: var(--color-text-primary);
+}
+
+.coming-soon {
+    display: flex;
+    flex-direction: column;
+    align-items: center;
+    justify-content: center;
+    padding: 60px 20px;
+    background: #f9f9f9;
+    border: 1px dashed #ccc;
+    border-radius: 8px;
+    text-align: center;
+}
+
+.coming-soon-icon {
+    width: 64px;
+    height: 64px;
+    margin-bottom: 20px;
+    opacity: 0.7;
+}
+
+.coming-soon p {
+    font-size: 1.2em;
+    color: #666;
+}
+</style>