feat(frontend): 统一界面图标体系

frontend/src/features/workspace/WorkspaceView.vue

@@ -4,6 +4,8 @@ import { useWorkspaceStore } from '@/stores/workspace'
 import { useEditorStore } from '@/stores/editor'
 import EditorHeader from '@/features/editor/EditorHeader.vue'
 import EditorPane from '@/features/editor/EditorPane.vue'
+import { EditPen } from '@element-plus/icons-vue'
+import AppIcon from '@/components/common/AppIcon.vue'
 
 const workspaceStore = useWorkspaceStore()
 const editorStore = useEditorStore()
@@ -28,7 +30,7 @@ onMounted(() => {
     </template>
     <div v-else class="empty-workspace">
       <div class="empty-content">
-        <div class="empty-icon">📝</div>
+        <AppIcon class="empty-icon" :icon="EditPen" :size="48" />
         <h2>开始写作</h2>
         <p>从左侧文件树选择笔记，或创建新的笔记</p>
       </div>