feat: use nuxt 4 structure

app/components/DarkToggle.vue

@@ -0,0 +1,21 @@
+<script setup lang="ts">
+const color = useColorMode()
+
+useHead({
+  meta: [{
+    id: 'theme-color',
+    name: 'theme-color',
+    content: () => color.value === 'dark' ? '#222222' : '#ffffff',
+  }],
+})
+
+function toggleDark() {
+  color.preference = color.value === 'dark' ? 'light' : 'dark'
+}
+</script>
+
+<template>
+  <button class="!outline-none" @click="toggleDark">
+    <div class="i-carbon-sun dark:i-carbon-moon" />
+  </button>
+</template>