feat(desktop-client): 阶段4-6 Electron EXE 客户端（登录/课表/作业/通知/成绩/设置 + Socket.IO 实时 + IndexedDB 离线缓存与自动同步 + electron-builder 打包）

packages/desktop-client/index.html

@@ -0,0 +1,13 @@
+<!doctype html>
+<html lang="zh-CN">
+  <head>
+    <meta charset="UTF-8" />
+    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
+    <!-- Electron 渲染进程安全策略：只允许加载本地资源与后端 HTTP/WS 连接 -->
+    <title>班级小助手</title>
+  </head>
+  <body>
+    <div id="app"></div>
+    <script type="module" src="/src/renderer/main.ts"></script>
+  </body>
+</html>