Initial commit: RustDesk 1.4.7 macOS desktop port

- Filled empty libs/hbb_common/ submodule (cloned from rustdesk/hbb_common)
- Patched Flutter 3.44 / Dart 3.12 compatibility:
  * flutter/lib/generated_bridge.dart: asTypedList with cast<>, DartPort=Int64
  * flutter/lib/common.dart: DialogTheme->DialogThemeData, TabBarTheme->TabBarThemeData
  * flutter/pubspec.yaml: extended_text 14.0.0->15.0.2, google_fonts override 5.0.0
  * flutter/macos/Runner/Configs/Release.xcconfig: EXCLUDED_ARCHS=x86_64
- Build verified: cargo check + cargo build --features flutter + cargo build --release --features flutter
- Verified flutter build macos --debug and --release both produce working .app
- Verified .dmg installer (27MB arm64) created via hdiutil
- Build deps: Xcode 26.5, CocoaPods 1.16.2, Flutter 3.44, VCPKG arm64-osx

flutter/lib/web/web_unique.dart

@@ -0,0 +1,30 @@
+import 'dart:async';
+import 'dart:convert';
+import 'dart:js' as js;
+
+Future<void> webselectFiles({required bool is_folder}) async {
+  return Future(
+      () => js.context.callMethod('setByName', ['select_files', is_folder]));
+}
+
+Future<void> webSendLocalFiles(
+    {required int handleIndex,
+    required int actId,
+    required String path,
+    required String to,
+    required int fileNum,
+    required bool includeHidden,
+    required bool isRemote}) {
+  return Future(() => js.context.callMethod('setByName', [
+        'send_local_files',
+        jsonEncode({
+          'id': actId,
+          'handle_index': handleIndex,
+          'path': path,
+          'to': to,
+          'file_num': fileNum,
+          'include_hidden': includeHidden,
+          'is_remote': isRemote,
+        })
+      ]));
+}