feat(mobile): 优化移动端头部功能

- 在移动端标题栏添加登录按钮，未登录时显示- 实现移动端标题栏点击返回主页功能
- 调整移动端搜索栏样式

biji-qianduan/src/components/HomePage.vue

@@ -120,10 +120,13 @@
             <el-button @click="isCollapsed = !isCollapsed" text circle class="mobile-menu-toggle">
               <el-icon size="24"><Menu /></el-icon>
             </el-button>
-            <h1 class="mobile-title">我的笔记</h1>
+            <h1 class="mobile-title" @click="resetToHomeView">我的笔记</h1>
             <el-button text circle class="mobile-search-toggle" @click="handleSearch">
               <el-icon size="22"><Search /></el-icon>
             </el-button>
+            <el-button v-if="!userStore.isLoggedIn" text circle class="mobile-login-toggle" @click="goToLogin">
+              <el-icon size="24"><User /></el-icon>
+            </el-button>
           </el-header>
 
           <!-- Mobile Search Bar -->
@@ -335,7 +338,7 @@ import {
   generateRegistrationCode,
   updatePassword
 } from '@/api/CommonApi.js'
-import { Plus, Fold, Expand, Folder, Document, Search, Edit, Delete, ArrowDown, Clock, Lock, InfoFilled, Menu } from "@element-plus/icons-vue";
+import { Plus, Fold, Expand, Folder, Document, Search, Edit, Delete, ArrowDown, Clock, Lock, InfoFilled, Menu, User } from "@element-plus/icons-vue";
 import { useUserStore } from '../stores/user';
 import { useRouter } from 'vue-router';
 import { privateNoteContent } from '../utils/privateNoteContent.js';
@@ -1268,6 +1271,16 @@ const resetUpdatePasswordForm = () => {
 }
 </style>
 
+.mobile-title {
+  cursor: pointer;
+}
+.mobile-search-container {
+.mobile-search-container {
+  margin-bottom: 1.5rem;
+}
+  padding: 0 1.5rem;
+  margin-bottom: 1.5rem;
+}
 <style scoped>
 /* 整体布局 */
 .home-page {