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/vcpkg/opus/fix-pkgconfig-version.patch

@@ -0,0 +1,15 @@
+diff --git a/cmake/OpusPackageVersion.cmake b/cmake/OpusPackageVersion.cmake
+index 447ce3b..15ebd8e 100644
+--- a/cmake/OpusPackageVersion.cmake
++++ b/cmake/OpusPackageVersion.cmake
+@@ -4,7 +4,9 @@ endif()
+ set(__opus_version INCLUDED)
+ 
+ function(get_package_version PACKAGE_VERSION PROJECT_VERSION)
+-
++  set(PACKAGE_VERSION "0" CACHE STRING "opus package version")
++  set(PROJECT_VERSION "0" CACHE STRING "opus project version")
++  return()
+   find_package(Git)
+   if(GIT_FOUND AND EXISTS "${CMAKE_CURRENT_LIST_DIR}/.git")
+     execute_process(COMMAND ${GIT_EXECUTABLE}