feat(i18n): add internationalization support

This commit introduces internationalization (i18n) support by integrating the `@nuxtjs/i18n` module. It configures English (en) and
Simplified Chinese (zh-CN) locales, adds a language selector to the header, and internationalizes the index page content using
translation files.

app/pages/index.vue

@@ -1,6 +1,19 @@
 <template>
   <UPage>
-    <UPageSection title="Trusted by">
+    <UHeader>
+      <template #title> Tootaio Studio </template>
+      <template #right>
+        <ULocaleSelect
+          :model-value="locale"
+          :locales="[en, zh_cn]"
+          @update:model-value="(v) => setLocale(v as 'en' | 'zh-CN')"
+        />
+      </template>
+    </UHeader>
+    <UPageSection
+      title="Trusted by"
+      :description="$t('index.trustedBy', { count: 10000 })"
+    >
       <UMarquee>
         <img
           v-for="logo in trustedBy"
@@ -15,6 +28,9 @@
 </template>
 
 <script lang="ts" setup>
+import { en, zh_cn } from "@nuxt/ui/locale";
+const { locale, setLocale } = useI18n();
+
 const trustedBy = ref([
   { src: "/index/trusted-by/logoipsum-284.svg", alt: "Logo Ipsum" },
   { src: "/index/trusted-by/logoipsum-338.svg", alt: "Logo Ipsum" },