refactor: replace all emoji icons with Element Plus SVG icons

Use @element-plus/icons-vue components for consistent, scalable vector
icons across sidebar navigation, section headers, ratings, and buttons.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/src/views/Layout.vue

@@ -10,6 +10,7 @@ import WorkScheduleModal from '@/components/team/WorkScheduleModal.vue'
 import NotificationPanel from '@/components/common/NotificationPanel.vue'
 import CreateGroupDialog from '@/components/group/CreateGroupDialog.vue'
 import JoinGroupDialog from '@/components/group/JoinGroupDialog.vue'
+import { Monitor, HomeFilled, Grid, Link, AlarmClock, SwitchButton, Bell, Plus } from '@element-plus/icons-vue'
 
 const router = useRouter()
 const route = useRoute()
@@ -55,18 +56,18 @@ function goHome() {
     <aside class="sidebar">
       <div class="sidebar-top">
         <div class="logo" @click="goHome">
-          <span class="logo-icon">🎮</span>
+          <el-icon class="logo-icon"><Monitor /></el-icon>
           <span class="logo-text">Game Group</span>
         </div>
       </div>
 
       <nav class="sidebar-nav">
         <router-link to="/" class="nav-item" active-class="nav-item--active">
-          <span class="nav-icon">🏠</span>
+          <el-icon class="nav-icon"><HomeFilled /></el-icon>
           <span>首页</span>
         </router-link>
         <router-link to="/games" class="nav-item" active-class="nav-item--active">
-          <span class="nav-icon">🎯</span>
+          <el-icon class="nav-icon"><Grid /></el-icon>
           <span>游戏库</span>
         </router-link>
       </nav>
@@ -77,8 +78,8 @@ function goHome() {
         <div class="section-header">
           <span class="section-title">我的群组</span>
           <div class="section-actions">
-            <button class="section-btn" @click="showCreateGroup = true" title="创建群组">+</button>
-            <button class="section-btn" @click="showJoinGroup = true" title="加入群组">&#x1F517;</button>
+            <button class="section-btn" @click="showCreateGroup = true" title="创建群组"><el-icon><Plus /></el-icon></button>
+            <button class="section-btn" @click="showJoinGroup = true" title="加入群组"><el-icon><Link /></el-icon></button>
           </div>
         </div>
         <div v-if="groupStore.groups.length === 0" class="empty-groups">
@@ -101,7 +102,7 @@ function goHome() {
         <div class="user-section">
           <StatusToggle />
           <button class="schedule-btn" @click="showScheduleModal = true" title="设置工作时间">
-            ⏰
+            <el-icon><AlarmClock /></el-icon>
           </button>
         </div>
         <div class="user-info">
@@ -112,7 +113,7 @@ function goHome() {
           />
           <span class="user-name">{{ userStore.user?.username }}</span>
           <button class="logout-btn" @click="handleLogout" title="退出登录">
-            🚪
+            <el-icon><SwitchButton /></el-icon>
           </button>
         </div>
       </div>
@@ -129,7 +130,7 @@ function goHome() {
             <span v-if="notificationStore.unreadCount > 0" class="badge">
               {{ notificationStore.unreadCount }}
             </span>
-            🔔
+            <el-icon><Bell /></el-icon>
           </button>
         </div>
       </header>