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/fdroid/patches/0000-flutter-android-x86.patch

@@ -0,0 +1,16 @@
+diff --git a/flutter-sdk/.gclient b/flutter-sdk/.gclient
+new file mode 100644
+index 0000000..fd12886
+--- /dev/null
++++ b/flutter-sdk/.gclient
+@@ -0,0 +1,10 @@
++solutions = [
++  {
++    "managed": False,
++    "name": "src/flutter",
++    "url": "https://github.com/flutter/engine.git@FLUTTER_VERSION_PLACEHOLDER",
++    "custom_deps": {},
++    "deps_file": "DEPS",
++    "safesync_url": "",
++  },
++]