refactor(login): 优化登录页面布局和功能

- 调整验证码重新发送和返回按钮的布局
- 添加返回按钮，提高用户操作便利性
- 优化代码结构，提高页面可维护性

app/pages/login/index.vue

@@ -176,18 +176,20 @@ const goLogin =async () => {
             <div class="text-[16px] text-[#000]">+{{ selectedZone }} {{ phoneNum }}</div>
           </div>
           <van-password-input :value="code" :gutter="10" :mask="false" focused @focus="showKeyboard = true" />
-          <div :class="`${countdown>0?'text-#BDBDBD':'text-#2B53AC'}  text-14px`">
-            {{ $t('login.reSend') }}<span v-if="countdown>0">({{countdown}})</span>
-          </div>
+       <div class="flex justify-between">
+         <div :class="`${countdown>0?'text-#BDBDBD':'text-#2B53AC'}  text-14px`">
+           {{ $t('login.reSend') }}<span v-if="countdown>0">({{countdown}})</span>
+         </div>
+         <div @click="goBack" class="text-#2B53AC text-14px">
+           {{ $t('login.back') }}
+         </div>
+       </div>
           <div class="mt-[17px]">
             <van-button v-if="code.length === 6" type="primary" block :loading="loadingRef.loading2" :loading-text="$t('login.login')" style="height: 48px" @click="goLogin">{{
                 $t('login.login')
               }}</van-button>
             <van-button v-else type="primary" color="#D3D3D3" block style="height: 48px">{{ $t('login.login') }}</van-button>
           </div>
-          <div class="mt-[17px]">
-            <van-button type="primary" @click="goBack" block style="height: 48px">{{ $t('login.back') }}</van-button>
-          </div>
         </div>
       </van-swipe-item>
     </van-swipe>