refactor: 确立独立子工程架构 (backend, admin, mpuniapp) 并同步更新 AGENTS.md 规范

admin/index.html

@@ -0,0 +1,18 @@
+<!DOCTYPE html>
+<html lang="en">
+  <head>
+    <meta charset="UTF-8" />
+    <link
+      rel="shortcut icon"
+      type="image/x-icon"
+      href="https://unpkg.byted-static.com/latest/byted/arco-config/assets/favicon.ico"
+    />
+    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
+    <meta http-equiv="X-UA-Compatible" content="ie=edge" />
+    <title>Arco Design Pro - 开箱即用的中台前端/设计解决方案</title>
+  </head>
+  <body>
+    <div id="root"></div>
+    <script type="module" src="/src/main.tsx"></script>
+  </body>
+</html>