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/CustomActions.def

@@ -0,0 +1,16 @@
+LIBRARY "CustomActions"
+
+EXPORTS
+    CustomActionHello
+    RemoveRuntimeGeneratedFiles
+    TerminateProcesses
+    AddFirewallRules
+    SetPropertyIsServiceRunning
+    TryStopDeleteService
+    CreateStartService
+    TryDeleteStartupShortcut
+    SetPropertyFromConfig
+    AddRegSoftwareSASGeneration
+    RemoveAmyuniIdd
+    InstallPrinter
+    UninstallPrinter