feat(i18n): 集成 vue-i18n 并配置多语言支持

(cherry picked from commit 15c9509318dd7d48c081c4ae4846598d9affb344)

src/pages/demos/i18n-demo.page.vue

@@ -0,0 +1,34 @@
+<script setup lang="ts">
+definePage({
+  meta: {
+    title: '国际化示例',
+  },
+});
+const { t, locale } = useI18n();
+
+function setLocale(newLocale: 'en-US' | 'zh-CN') {
+  locale.value = newLocale;
+}
+</script>
+
+<template>
+  <div class="p-4">
+    <n-h1>{{ t('page.i18n-demo.title') }}</n-h1>
+
+    <n-card :title="t('page.i18n-demo.change-language')">
+      <n-p>
+        {{ t('page.i18n-demo.current-language') }}:
+        <span class="font-bold">{{ locale }}</span>
+      </n-p>
+
+      <n-p>
+        {{ t('page.i18n-demo.hello', { name: 'Kilo' }) }}
+      </n-p>
+
+      <n-space>
+        <n-button type="primary" @click="setLocale('en-US')"> English </n-button>
+        <n-button type="success" @click="setLocale('zh-CN')"> 简体中文 </n-button>
+      </n-space>
+    </n-card>
+  </div>
+</template>