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_text.dart

@@ -0,0 +1,46 @@
+import 'package:flutter/material.dart';
+import 'package:openim_common/openim_common.dart';
+
+class ChatText extends StatelessWidget {
+  const ChatText({
+    Key? key,
+    this.isISend = false,
+    required this.text,
+    this.prefixSpan,
+    this.patterns = const <MatchPattern>[],
+    this.textAlign = TextAlign.left,
+    this.overflow = TextOverflow.clip,
+    this.textStyle,
+    this.maxLines,
+    this.textScaleFactor = 1.0,
+    this.model = TextModel.match,
+    this.onVisibleTrulyText,
+  }) : super(key: key);
+  final bool isISend;
+  final String text;
+  final TextStyle? textStyle;
+  final InlineSpan? prefixSpan;
+  final TextAlign textAlign;
+  final TextOverflow overflow;
+  final int? maxLines;
+  final double textScaleFactor;
+  final List<MatchPattern> patterns;
+  final TextModel model;
+  final Function(String? text)? onVisibleTrulyText;
+
+  @override
+  Widget build(BuildContext context) => MatchTextView(
+        text: text,
+        textStyle: textStyle ??
+            (isISend ? Styles.ts_FFFFFF_17sp : Styles.ts_0C1C33_17sp),
+        matchTextStyle: Styles.ts_0089FF_17sp,
+        prefixSpan: prefixSpan,
+        textAlign: textAlign,
+        overflow: overflow,
+        textScaleFactor: textScaleFactor,
+        patterns: patterns,
+        model: model,
+        maxLines: maxLines,
+        onVisibleTrulyText: onVisibleTrulyText,
+      );
+}