fronted/src/components/auth/AuthThemeToggle.vue

<template>
  <button
    type="button"
    class="theme-toggle-btn fixed right-4 top-4 z-50"
    :title="ui.theme === 'dark' ? 'Chế độ sáng' : 'Chế độ tối'"
    @click="ui.toggleTheme()"
  >
    <svg v-if="ui.theme === 'dark'" width="16" height="16" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"><circle cx="12" cy="12" r="5"/><line x1="12" y1="1" x2="12" y2="3"/><line x1="12" y1="21" x2="12" y2="23"/><line x1="4.22" y1="4.22" x2="5.64" y2="5.64"/><line x1="18.36" y1="18.36" x2="19.78" y2="19.78"/><line x1="1" y1="12" x2="3" y2="12"/><line x1="21" y1="12" x2="23" y2="12"/><line x1="4.22" y1="19.78" x2="5.64" y2="18.36"/><line x1="18.36" y1="5.64" x2="19.78" y2="4.22"/></svg>
    <svg v-else width="16" height="16" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"><path d="M21 12.79A9 9 0 1 1 11.21 3 7 7 0 0 0 21 12.79z"/></svg>
  </button>
</template>

<script setup>
import { useUiStore } from '@/stores/ui.js'

const ui = useUiStore()
</script>