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/vcpkg.json

@@ -0,0 +1,44 @@
+{
+  "name": "ffmpeg",
+  "version": "7.1",
+  "port-version": 1,
+  "description": [
+    "a library to decode, encode, transcode, mux, demux, stream, filter and play pretty much anything that humans and machines have created.",
+    "FFmpeg is the leading multimedia framework, able to decode, encode, transcode, mux, demux, stream, filter and play pretty much anything that humans and machines have created. It supports the most obscure ancient formats up to the cutting edge. No matter if they were designed by some standards committee, the community or a corporation. It is also highly portable: FFmpeg compiles, runs, and passes our testing infrastructure FATE across Linux, Mac OS X, Microsoft Windows, the BSDs, Solaris, etc. under a wide variety of build environments, machine architectures, and configurations."
+  ],
+  "homepage": "https://ffmpeg.org",
+  "license": null,
+  "dependencies": [
+    {
+      "name": "vcpkg-cmake-get-vars",
+      "host": true
+    },
+    {
+      "name": "vcpkg-pkgconfig-get-modules",
+      "host": true
+    }
+  ],
+  "default-features": [
+  ],
+  "features": {
+    "amf": {
+      "description": "AMD AMF codec support",
+      "dependencies": [
+        "amd-amf"
+      ]
+    },
+    "nvcodec": {
+      "description": "Nvidia video decoding/encoding acceleration",
+      "supports": "linux | (!osx & !uwp & !(arm64 & windows))",
+      "dependencies": [
+        "ffnvcodec"
+      ]
+    },
+    "qsv": {
+      "description": "Intel QSV Codec",
+      "dependencies": [
+        "mfx-dispatch"
+      ]
+    }
+  }
+}