feat(mobile-next): 导入官方 openim-flutter-demo 固定基线 3.8.3-patch.3 并完成双构建

- 上游: github.com/OpenIMSDK/openim-flutter-demo tag 3.8.3-patch.3
  commit b3dfdb1e8aaeaaf6f0793e10cadd20d5c184a31f
- 并行目录 mobile-next/ 原样导入（含 LICENSE），不覆盖现网 mobile/
- 锁定 Flutter 3.24.5 / Dart 3.5.4 / JDK 17 / Gradle 7.6.3 / AGP 7.3.1
- 实测 Android debug 与 release 构建均成功（见 docs/mobile-next-baseline-import.md）
- 本提交可单独回退：git revert 1db1229（重写前）

Co-authored-by: multica-agent <github@multica.ai>

mobile-next/CONFIGKEY.md

@@ -0,0 +1,88 @@
+
+# Common Function Configuration Guide
+
+- [Offline push](#offlinepush)
+- [Map](#map)
+
+## Offlinepush
+
+Currently using the integrated solution.
+
+### Client configuration
+
+#### 1. Use Getui (https://getui.com/) in mainland China
+
+###### Configure iOS and Android in the integration guide of Getui
+
+**iOS platform configuration:**
+According to [its documentation](https://docs.getui.com/getui/mobile/ios/overview/), make the corresponding iOS configuration. Then find the following files in the code and modify the corresponding iOS side key:
+
+- **[push_controller.dart](openim_common/lib/src/controller/push_controller.dart)**
+
+```dart
+  const appID = 'your-app-id';
+  const appKey = 'your-app-key';
+  const appSecret = 'your-app-secret';
+```
+
+**Android platform configuration:**
+According to [its documentation](https://docs.getui.com/getui/mobile/android/overview/), make corresponding Android configurations, and pay attention to [multi-vendor](https://docs.getui.com/getui/mobile/vendor/vendor_open/) configurations. Then modify the following file contents:
+
+- **[build.gradle](android/app/build.gradle)**
+
+```gradle
+  manifestPlaceholders = [
+      GETUI_APPID    : "",
+      XIAOMI_APP_ID  : "",
+      XIAOMI_APP_KEY : "",
+      MEIZU_APP_ID   : "",
+      MEIZU_APP_KEY  : "",
+      HUAWEI_APP_ID  : "",
+      OPPO_APP_KEY   : "",
+      OPPO_APP_SECRET: "",
+      VIVO_APP_ID    : "",
+      VIVO_APP_KEY   : "",
+      HONOR_APP_ID   : "",
+  ]
+```
+
+#### 2. Use [FCM (Firebase Cloud Messaging)](https://firebase.google.com/docs/cloud-messaging) in overseas regions
+
+According to the integration guide of [FCM](https://firebase.google.com/docs/cloud-messaging), replace the following files:
+
+- **[google-services.json](android/app/google-services.json)** (Android platform)
+- **[GoogleService-Info.plist](ios/Runner/GoogleService-Info.plist)** (iOS platform)
+- **[firebase_options.dart](openim_common/lib/src/controller/firebase_options.dart)** (Firebase configuration in Dart project)
+
+### Offline push banner settings
+
+Currently, the SDK is designed to directly control the display content of the push banner by the client. When sending a message, set the input parameter [offlinePushInfo](https://github.com/openimsdk/openim-flutter-demo/blob/cc72b6d7ca5f70ca07885857beecec512f904f8c/lib/pages/chat/chat_logic.dart#L543):
+
+```dart
+  final offlinePushInfo = OfflinePushInfo(
+  title: "Fill in the title",
+  desc: "Fill in the description, such as the message content",
+  iOSBadgeCount: true,
+  );
+  // If you do not customize offlinePushInfo, the title defaults to the app name, and the desc defaults to "You received a new message"
+```
+
+According to actual needs, you can enable the offline push function after completing the corresponding client and server configurations.
+
+---
+
+## Map
+
+### Configuration Guide
+
+Need to configure the corresponding AMap Key. Please refer to [AMap Document](https://lbs.amap.com/) for details. The code in the project needs to modify the following Key:
+
+- **[webKey](https://github.com/openimsdk/openim-flutter-demo/blob/5720a10a31a0a9bc5319775f9f4da83d6996dbfe/openim_common/lib/src/config.dart#L49)**
+- **[webServerKey](https://github.com/openimsdk/openim-flutter-demo/blob/5720a10a31a0a9bc5319775f9f4da83d6996dbfe/openim_common/lib/src/config.dart#L50)**
+
+```dart
+  static const webKey = 'webKey';
+  static const webServerKey = 'webServerKey';
+```
+
+Once the configuration is complete, you can enable the map function.