Add macos (part 1)

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

macos/Runner/AppDelegate.swift

@@ -0,0 +1,13 @@
+import Cocoa
+import FlutterMacOS
+
+@main
+class AppDelegate: FlutterAppDelegate {
+  override func applicationShouldTerminateAfterLastWindowClosed(_ sender: NSApplication) -> Bool {
+    return true
+  }
+
+  override func applicationSupportsSecureRestorableState(_ app: NSApplication) -> Bool {
+    return true
+  }
+}

macos/Runner/Assets.xcassets/AppIcon.appiconset/Contents.json

@@ -0,0 +1,68 @@
+{
+    "info": {
+        "version": 1,
+        "author": "xcode"
+    },
+    "images": [
+        {
+            "size": "16x16",
+            "idiom": "mac",
+            "filename": "app_icon_16.png",
+            "scale": "1x"
+        },
+        {
+            "size": "16x16",
+            "idiom": "mac",
+            "filename": "app_icon_32.png",
+            "scale": "2x"
+        },
+        {
+            "size": "32x32",
+            "idiom": "mac",
+            "filename": "app_icon_32.png",
+            "scale": "1x"
+        },
+        {
+            "size": "32x32",
+            "idiom": "mac",
+            "filename": "app_icon_64.png",
+            "scale": "2x"
+        },
+        {
+            "size": "128x128",
+            "idiom": "mac",
+            "filename": "app_icon_128.png",
+            "scale": "1x"
+        },
+        {
+            "size": "128x128",
+            "idiom": "mac",
+            "filename": "app_icon_256.png",
+            "scale": "2x"
+        },
+        {
+            "size": "256x256",
+            "idiom": "mac",
+            "filename": "app_icon_256.png",
+            "scale": "1x"
+        },
+        {
+            "size": "256x256",
+            "idiom": "mac",
+            "filename": "app_icon_512.png",
+            "scale": "2x"
+        },
+        {
+            "size": "512x512",
+            "idiom": "mac",
+            "filename": "app_icon_512.png",
+            "scale": "1x"
+        },
+        {
+            "size": "512x512",
+            "idiom": "mac",
+            "filename": "app_icon_1024.png",
+            "scale": "2x"
+        }
+    ]
+}