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/Home.vue

@@ -10,6 +10,7 @@ import { UserStatusMap } from '@/types'
 import type { Game } from '@/types'
 import TeamSessionPanel from '@/components/team/TeamSessionPanel.vue'
 import IdleMembersList from '@/components/team/IdleMembersList.vue'
+import { User, Promotion, TrendCharts } from '@element-plus/icons-vue'
 
 const router = useRouter()
 const groupStore = useGroupStore()
@@ -72,11 +73,11 @@ function openGameDetail(game: Game) {
       <!-- 左列: 我的群组 -->
       <section class="section groups-section">
         <h2 class="section-title">
-          <span class="section-icon">&#x1F3AE;</span> 我的群组
+          <el-icon class="section-icon"><User /></el-icon> 我的群组
         </h2>
 
         <div v-if="groupStore.groups.length === 0" class="empty-state">
-          <div class="empty-icon">&#x1F3AE;</div>
+          <div class="empty-icon"><el-icon :size="40"><User /></el-icon></div>
           <p class="empty-text">暂无群组</p>
           <p class="empty-hint">创建或加入一个群组，开始组队冒险吧</p>
         </div>
@@ -100,7 +101,7 @@ function openGameDetail(game: Game) {
       <!-- 右列: 当前临时小组 -->
       <section class="section session-section">
         <h2 class="section-title">
-          <span class="section-icon">&#x2694;</span> 当前临时小组
+          <el-icon class="section-icon"><Promotion /></el-icon> 当前临时小组
         </h2>
         <div class="session-card">
           <TeamSessionPanel />
@@ -115,7 +116,7 @@ function openGameDetail(game: Game) {
     <!-- 热门游戏 -->
     <section class="section games-section">
       <h2 class="section-title">
-        <span class="section-icon">&#x1F525;</span> 热门游戏
+        <span class="section-icon"><el-icon><TrendCharts /></el-icon></span> 热门游戏
       </h2>
 
       <div v-if="loading" class="loading-state">
@@ -124,7 +125,7 @@ function openGameDetail(game: Game) {
       </div>
 
       <div v-else-if="popularGames.length === 0" class="empty-state">
-        <div class="empty-icon">&#x1F3AE;</div>
+        <div class="empty-icon"><el-icon :size="40"><TrendCharts /></el-icon></div>
         <p class="empty-text">暂无热门游戏</p>
       </div>