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/ffmpeg/0043-fix-miss-head.patch

@@ -0,0 +1,12 @@
+diff --git a/libavfilter/textutils.c b/libavfilter/textutils.c
+index ef658d0..c61b0ad 100644
+--- a/libavfilter/textutils.c
++++ b/libavfilter/textutils.c
+@@ -31,6 +31,7 @@
+ #include "libavutil/file.h"
+ #include "libavutil/mem.h"
+ #include "libavutil/time.h"
++#include "libavutil/time_internal.h"
+ 
+ static int ff_expand_text_function_internal(FFExpandTextContext *expand_text, AVBPrint *bp,
+                                             char *name, unsigned argc, char **argv)