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/xorg.conf

@@ -0,0 +1,30 @@
+Section "Monitor"
+    Identifier "Dummy Monitor"
+ 
+    # Default HorizSync 31.50 - 48.00 kHz
+    HorizSync 5.0 - 150.0
+    # Default VertRefresh 50.00 - 70.00 Hz
+    VertRefresh 5.0 - 100.0
+ 
+    # Taken from https://www.xpra.org/xorg.conf
+    Modeline "1920x1080" 23.53 1920 1952 2040 2072 1080 1106 1108 1135
+    Modeline "1280x720" 27.41 1280 1312 1416 1448 720 737 740 757
+EndSection
+ 
+Section "Device"
+    Identifier "Dummy VideoCard"
+    Driver "dummy"
+    # Default VideoRam 4096
+    # (1920 * 1080 * 4) / 1024 = 8100
+    VideoRam 8100
+EndSection
+ 
+Section "Screen"
+    Identifier "Dummy Screen"
+    Device "Dummy VideoCard"
+    Monitor "Dummy Monitor"
+    SubSectionSub "Display"
+        Depth 24
+        Modes "1920x1080" "1280x720"
+    EndSubSection
+EndSection