feat: 在多个页面添加导航栏组件

- 创建可复用的导航栏组件 navBar.vue
- 在 second、coupon、badge、third 等页面引入导航栏
- 提供统一的返回按钮功能，提升用户体验

src/components/navBar.vue

+<script setup>
+const handleBack = () => {
+    uni.navigateBack();
+};
+</script>
+
+<template>
+    <view class="navbar">
+        <view class="navbar-left" @click="handleBack">
+            <up-icon name="arrow-left" size="40rpx" color="#2D4B5D"></up-icon>
+        </view>
+    </view>
+</template>
+
+<style lang="scss" scoped>
+.navbar {
+    position: fixed;
+    top: 0;
+    left: 0;
+    width: 100%;
+    height: 176rpx;
+    z-index: 100;
+    display: flex;
+    align-items: flex-end;
+    padding-bottom: 20rpx;
+    box-sizing: border-box;
+}
+
+.navbar-left {
+    padding-left: 32rpx;
+    display: flex;
+    align-items: center;
+}
+</style>

src/pages/badge/index.vue

 <script setup>
 import { ref, computed } from 'vue';
+import navBar from '@/components/navBar.vue';
 
 const ASSETS = Object.freeze({
     blank: '/static/badge/blank.webp',
@@ -65,6 +66,7 @@ const navToContinuePage = () => {
 
 <template>
     <view class="container">
+        <navBar />
         <view class="title-box">
             <view class="title-content">
                 <view class="title">我的徽章</view>

src/pages/coupon/index.vue

 <script setup>
 import { ref } from 'vue';
+import navBar from '@/components/navBar.vue';
 
 const ASSETS = Object.freeze({
     bg: '/static/coupon/bg.webp',
@@ -100,6 +101,7 @@ const toggleExpand = (coupon) => {
 
 <template>
     <view class="container">
+        <navBar />
         <view class="title">我的优惠券</view>
         <scroll-view scroll-y class="coupon-list">
             <view 

src/pages/second/index.vue

 <script setup>
+import navBar from '@/components/navBar.vue';
+
 const ASSETS = Object.freeze({
   bg: '/static/second/bg.webp',
   info: '/static/second/info.webp',
@@ -16,6 +18,7 @@ const handleNext = () => {
 
 <template>
   <view class="container">
+    <navBar />
     <!-- 主体内容 -->
     <view class="main-content">
       <!-- 背景 -->

src/pages/second/part1.vue

 <script setup>
+import navBar from '@/components/navBar.vue';
+
 const ASSETS = Object.freeze({
   title: '/static/second/part1/title.webp',
   center: '/static/second/part1/center.webp',
@@ -12,6 +14,7 @@ const ASSETS = Object.freeze({
 
 <template>
   <view class="part1-container">
+    <navBar />
     <!-- 顶部标题 -->
     <view class="header-section">
       <image class="title-img" :src="ASSETS.title" mode="widthFix" />

src/pages/second/part2.vue

 <script setup>
 import { ref, onMounted, getCurrentInstance, computed } from 'vue';
 import { useDrag } from './hooks/useDrag';
+import navBar from '@/components/navBar.vue';
 
 const ASSETS = Object.freeze({
   title: '/static/second/part2/title.webp',
@@ -140,6 +141,7 @@ const getGhostIcon = () => {
 
 <template>
   <view class="part2-container">
+    <navBar />
     <!-- 拖拽时的镜像 -->
     <view 
       v-if="isDragging"

src/pages/second/part4/index.vue

 <script setup>
 import { ref, computed, onMounted, getCurrentInstance } from 'vue';
 import { useDrag } from '../hooks/useDrag';
+import navBar from '@/components/navBar.vue';
 
 const ASSETS = Object.freeze({
     box: '/static/second/part4/index/box.webp',
@@ -179,6 +180,7 @@ onMounted(() => {
 
 <template>
     <view class="part4-container">
+        <navBar />
         <!-- 拖拽镜像 -->
         <view v-if="isDragging" class="drag-ghost" :style="{ left: `${dragPosition.x}px`, top: `${dragPosition.y}px` }">
             <image :src="getGhostIcon()" mode="scaleToFill" :class="['ghost-icon', `ghost-${getDraggedType()}`]" />

src/pages/third/index.vue

 <script setup>
 import { ref } from 'vue';
 import { onLoad } from '@dcloudio/uni-app';
+import navBar from '@/components/navBar.vue';
 import Beaker from './components/beaker.vue';
 import TabsInstructionsPanel from './components/TabsInstructionsPanel.vue';
 import BottomActionBar from './components/BottomActionBar.vue';
@@ -61,6 +62,7 @@ const closeCompletion = () => {
 
 <template>
   <view class="container">
+    <navBar />
     <image class="bg" :src="assets.bg" mode="aspectFill" />
 
     <view class="header" :style="{ paddingTop: statusBarHeight + 'px' }">