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/lib/widgets/screen_lock_title.dart

@@ -0,0 +1,31 @@
+import 'package:flutter/material.dart';
+import 'package:openim_common/openim_common.dart';
+import 'package:sprintf/sprintf.dart';
+
+class ScreenLockTitle extends StatelessWidget {
+  const ScreenLockTitle({
+    Key? key,
+    required this.stream,
+  }) : super(key: key);
+
+  final Stream<String> stream;
+
+  @override
+  Widget build(BuildContext context) {
+    return Column(children: [
+      Text(StrRes.plsEnterPassword, style: Styles.ts_FFFFFF_17sp),
+      StreamBuilder(
+        builder: (context, AsyncSnapshot<String?> snapshot) {
+          if (snapshot.hasData) {
+            return Text(
+              sprintf(StrRes.lockPwdErrorHint, [snapshot.data]),
+              style: Styles.ts_FF381F_17sp,
+            );
+          }
+          return const SizedBox();
+        },
+        stream: stream,
+      ),
+    ]);
+  }
+}