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/openim_common/lib/src/widgets/chat/chat_radio.dart

@@ -0,0 +1,27 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_screenutil/flutter_screenutil.dart';
+import 'package:openim_common/openim_common.dart';
+
+class ChatRadio extends StatelessWidget {
+  const ChatRadio({
+    Key? key,
+    required this.checked,
+    this.onTap,
+    this.enabled = true,
+  }) : super(key: key);
+  final bool checked;
+  final Function()? onTap;
+  final bool enabled;
+
+  @override
+  Widget build(BuildContext context) {
+    return GestureDetector(
+      behavior: HitTestBehavior.translucent,
+      child:
+          (checked || !enabled ? ImageRes.radioSel : ImageRes.radioNor).toImage
+            ..width = 20.w
+            ..height = 20.h
+            ..opacity = (enabled ? 1 : .5),
+    );
+  }
+}