feat: 小程序移除管理后台入口，新增admin-web前端项目

将管理后台功能从微信小程序中剥离，独立为Vue.js前端项目admin-web

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

admin-web/README.md

@@ -0,0 +1,24 @@
+# admin-web
+
+## Project setup
+```
+yarn install
+```
+
+### Compiles and hot-reloads for development
+```
+yarn serve
+```
+
+### Compiles and minifies for production
+```
+yarn build
+```
+
+### Lints and fixes files
+```
+yarn lint
+```
+
+### Customize configuration
+See [Configuration Reference](https://cli.vuejs.org/config/).