feat: add switch with zh|en

frontend/src/components/AppHeader.vue

@@ -0,0 +1,48 @@
+<template>
+  <header class="app-header">
+    <router-link to="/" class="logo-link">
+      <div class="logo">Email Unlimit</div>
+    </router-link>
+    <nav class="nav-links">
+      <a href="https://gitea.shenjianl.cn/shenjianZ/email-unlimit" target="_blank">Gitee</a>
+      <router-link to="/settings" class="settings-link" title="设置">
+        <img src="@/assets/setting.svg" alt="Settings" class="settings-icon" />
+      </router-link>
+    </nav>
+  </header>
+</template>
+
+<script>
+export default {
+  name: 'AppHeader',
+};
+</script>
+
+<style scoped>
+.logo-link {
+  text-decoration: none;
+}
+
+.nav-links {
+  display: flex;
+  align-items: center;
+  gap: 2rem;
+}
+
+.settings-link {
+  display: flex;
+  align-items: center;
+}
+
+.settings-icon {
+  width: 24px;
+  height: 24px;
+  transition: filter 0.3s ease;
+}
+
+.settings-link:hover .settings-icon {
+  /* Generated by https://codepen.io/sosuke/pen/Pjoqqp */
+  /* This filter converts black to the --primary-purple color */
+  filter: brightness(0) saturate(100%) invert(20%) sepia(80%) saturate(3750%) hue-rotate(261deg) brightness(95%) contrast(94%);
+}
+</style>