feat(i18n): add language switcher component to navigation

frontend/src/views/Home.vue

@@ -4,6 +4,7 @@
     <nav class="navbar">
       <div class="nav-brand">MIROFISH</div>
       <div class="nav-links">
+        <LanguageSwitcher dark />
         <a href="https://github.com/666ghj/MiroFish" target="_blank" class="github-link">
           访问我们的Github主页 <span class="arrow">↗</span>
         </a>
@@ -210,6 +211,7 @@
 import { ref, computed } from 'vue'
 import { useRouter } from 'vue-router'
 import HistoryDatabase from '../components/HistoryDatabase.vue'
+import LanguageSwitcher from '../components/LanguageSwitcher.vue'
 
 const router = useRouter()
 
@@ -351,6 +353,7 @@ const startSimulation = () => {
 .nav-links {
   display: flex;
   align-items: center;
+  gap: 16px;
 }
 
 .github-link {