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

res/msi/CustomActions/pch.h

@@ -0,0 +1,13 @@
+// pch.h: This is a precompiled header file.
+// Files listed below are compiled only once, improving build performance for future builds.
+// This also affects IntelliSense performance, including code completion and many code browsing features.
+// However, files listed here are ALL re-compiled if any one of them is updated between builds.
+// Do not add files here that you will be updating frequently as this negates the performance advantage.
+
+#ifndef PCH_H
+#define PCH_H
+
+// add headers that you want to pre-compile here
+#include "framework.h"
+
+#endif //PCH_H