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

flutter/macos/Runner/AppDelegate.swift

@@ -0,0 +1,24 @@
+import Cocoa
+import FlutterMacOS
+
+@main
+class AppDelegate: FlutterAppDelegate {
+    var launched = false;
+  override func applicationShouldTerminateAfterLastWindowClosed(_ sender: NSApplication) -> Bool {
+      dummy_method_to_enforce_bundling()
+    // https://github.com/leanflutter/window_manager/issues/214
+    return false
+  }
+    
+    override func applicationShouldOpenUntitledFile(_ sender: NSApplication) -> Bool {
+        if (launched) {
+            handle_applicationShouldOpenUntitledFile();
+        }
+        return true
+    }
+    
+    override func applicationDidFinishLaunching(_ aNotification: Notification) {
+        launched = true;
+        NSApplication.shared.activate(ignoringOtherApps: true);
+    }
+}