add color theme with dark and light mode!

src/components/ThemeToggle.vue

@@ -0,0 +1,38 @@
+<script setup lang="ts">
+import { ref, onMounted } from 'vue'
+import { Moon, Sun } from 'lucide-vue-next'
+import { Button } from '@/components/ui/button'
+
+const isDark = ref(false)
+
+const toggleTheme = () => {
+  isDark.value = !isDark.value
+  updateTheme()
+}
+
+const updateTheme = () => {
+  if (isDark.value) {
+    document.documentElement.classList.add('dark')
+    localStorage.setItem('theme', 'dark')
+  } else {
+    document.documentElement.classList.remove('dark')
+    localStorage.setItem('theme', 'light')
+  }
+}
+
+onMounted(() => {
+  const savedTheme = localStorage.getItem('theme')
+  isDark.value = 
+    savedTheme === 'dark' || 
+    (!savedTheme && window.matchMedia('(prefers-color-scheme: dark)').matches)
+  updateTheme()
+})
+</script>
+
+<template>
+  <Button variant="ghost" size="icon" @click="toggleTheme">
+    <Sun v-if="isDark" class="h-5 w-5" />
+    <Moon v-else class="h-5 w-5" />
+    <span class="sr-only">Toggle theme</span>
+  </Button>
+</template>