style(pc): replace emoji with Element Plus icons for consistency

- VoiceControls.vue: 🎤🔇🔊🔈🚪 → Microphone/Mute/Headset/SwitchButton
- GamesLibrary.vue: 🎮(无群组) → Monitor, 📦(空状态) → Box
  + brand color tint on empty-state icons

PC 占位图已与移动端共享 public/ 目录（自动一致）；
其余 30 个文件的 el-icon 是桌面端 Element Plus 合理约定，保留不动。

build verified: vue-tsc + vite build pass

frontend/src/components/voice/VoiceControls.vue

@@ -1,5 +1,7 @@
 <!-- src/components/voice/VoiceControls.vue -->
 <script setup lang="ts">
+import { Microphone, Mute, Headset, SwitchButton } from '@element-plus/icons-vue'
+
 defineProps<{
   micEnabled: boolean
   speakerEnabled: boolean
@@ -20,7 +22,7 @@ const emit = defineEmits<{
       :class="{ active: micEnabled, off: !micEnabled }"
       @click="emit('toggleMic')"
     >
-      <span class="ctrl-icon">{{ micEnabled ? '🎤' : '🔇' }}</span>
+      <el-icon class="ctrl-icon"><Microphone v-if="micEnabled" /><Mute v-else /></el-icon>
       <span class="ctrl-label">麦克风</span>
     </button>
 
@@ -29,12 +31,12 @@ const emit = defineEmits<{
       :class="{ active: speakerEnabled, off: !speakerEnabled }"
       @click="emit('toggleSpeaker')"
     >
-      <span class="ctrl-icon">{{ speakerEnabled ? '🔊' : '🔈' }}</span>
+      <el-icon class="ctrl-icon"><Headset /></el-icon>
       <span class="ctrl-label">扬声器</span>
     </button>
 
     <button class="ctrl-btn leave-btn" @click="emit('leave')">
-      <span class="ctrl-icon">🚪</span>
+      <el-icon class="ctrl-icon"><SwitchButton /></el-icon>
       <span class="ctrl-label">离开</span>
     </button>
   </div>
@@ -80,6 +82,9 @@ const emit = defineEmits<{
 
 .ctrl-icon {
   font-size: 22px;
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
 }
 
 .ctrl-label {

frontend/src/views/GamesLibrary.vue

@@ -9,7 +9,7 @@ import GameDetailDialog from '@/components/game/GameDetailDialog.vue'
 import GameFormDialog from '@/components/game/GameFormDialog.vue'
 import ImportGamesDialog from '@/components/game/ImportGamesDialog.vue'
 import { ElMessage, ElMessageBox } from 'element-plus'
-import { Close } from '@element-plus/icons-vue'
+import { Close, Monitor, Box } from '@element-plus/icons-vue'
 
 const groupStore = useGroupStore()
 
@@ -128,7 +128,7 @@ async function handleImportComplete() {
   <div class="games-library">
     <!-- 无群组引导 -->
     <div v-if="!hasGroups" class="no-group">
-      <div class="no-group-icon">🎮</div>
+      <div class="no-group-icon"><el-icon :size="56"><Monitor /></el-icon></div>
       <p class="no-group-text">还没有群组</p>
       <p class="no-group-hint">先创建或加入一个群组，然后就可以管理游戏库了</p>
     </div>
@@ -175,7 +175,7 @@ async function handleImportComplete() {
       <div v-if="loading" class="loading">加载中...</div>
 
       <div v-else-if="games.length === 0" class="empty">
-        <div class="empty-icon">📦</div>
+        <div class="empty-icon"><el-icon :size="48"><Box /></el-icon></div>
         <p class="empty-text">暂无游戏</p>
         <p class="empty-hint">点击「添加游戏」或「导入」开始管理游戏库</p>
       </div>
@@ -216,6 +216,8 @@ async function handleImportComplete() {
 .no-group-icon {
   font-size: 48px;
   margin-bottom: 16px;
+  color: var(--gg-primary);
+  opacity: 0.7;
 }
 
 .no-group-text {
@@ -317,6 +319,7 @@ async function handleImportComplete() {
 .empty-icon {
   font-size: 48px;
   margin-bottom: 12px;
+  color: var(--gg-text-muted);
 }
 
 .empty-text {