feat: update tabBar to 3 items, add qrcode page skeleton, rename app

Co-Authored-By: Claude <noreply@anthropic.com>

src/pages/profile/index.vue

@@ -6,7 +6,7 @@
       </view>
       <view class="user-info">
         <text class="nickname">{{ userStore.userInfo?.nickname || '未登录' }}</text>
-        <text class="user-desc" v-if="userStore.isLogin">欢迎使用湖南12301文旅专区</text>
+        <text class="user-desc" v-if="userStore.isLogin">欢迎使用爱上萍乡</text>
         <text class="user-desc" v-else @click="goLogin">点击登录</text>
       </view>
     </view>

src/pages/qrcode/index.vue

@@ -0,0 +1,12 @@
+<template>
+  <view class="page">
+    <text>入园码页面（开发中）</text>
+  </view>
+</template>
+
+<script setup lang="ts">
+</script>
+
+<style scoped>
+.page { min-height: 100vh; background: #f5f5f5; display: flex; align-items: center; justify-content: center; }
+</style>