Refactor H5 line management and cache handling in WebView app

- Introduced shared_preferences for initial H5 cache management.
- Added methods to clear H5 caches and probe line availability.
- Enhanced error handling for line loading and switching.
- Removed openim_common package and its configurations.
- Updated widget tests to reflect changes in H5 line handling and URL management.

README.md

@@ -1,25 +1,15 @@
 # im_webview_app
 
-Flutter WebView 套壳 App，默认加载：
-
-```text
-https://h5-test.imharry.work/
-```
+Flutter WebView 套壳 App，启动后会请求 `/client_config/query` 获取 H5 线路配置，并加载第一条可用线路。
 
 ## H5 线路切换
 
-线路切换在 Flutter 套壳层完成，H5 页面不需要承载线路切换逻辑。每条线路对应一个独立 WebView，切换时只切换当前显示的 WebView，不会改写 H5 页面运行中的请求地址。
-
-默认线路配置在：
-
-```text
-openim_common/lib/src/config.dart
-```
-
-也可以在打包时覆盖：
+线路切换在 Flutter 套壳层完成。远程配置不可用时，会先使用启动兜底线路；也可以在打包时覆盖启动线路或配置接口地址：
 
 ```bash
 flutter build apk --release --dart-define=H5_LINE_URLS=https://h5-one.example/,https://h5-two.example/
+flutter build apk --release --dart-define=CLIENT_CONFIG_QUERY_URL=https://api.example.com/client_config/query
+flutter build apk --release --dart-define=BOOTSTRAP_H5_LINE_URL=https://h5-one.example/
 ```
 
 ## 本地打包