Add the Metin2 app icon for Android, macOS and iOS

branding/icon/icon.svg (a cracked Metin stone with glowing runes, inside a studded gold ring, in front of
a blood moon over ink mountains) is the single source; build_icons.sh renders it with headless Chrome and
writes the committed outputs: Android legacy + adaptive mipmaps (wired into the manifest), the macOS
AppIcon.icns and the iOS AppIcon.appiconset. scripts/package_mac_app.sh wraps mt_native_render into a
local Metin2.app using that icon.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

branding/icon/ios/AppIcon.appiconset/Contents.json

@@ -0,0 +1,14 @@
+{
+  "images" : [
+    {
+      "filename" : "AppIcon-1024.png",
+      "idiom" : "universal",
+      "platform" : "ios",
+      "size" : "1024x1024"
+    }
+  ],
+  "info" : {
+    "author" : "xcode",
+    "version" : 1
+  }
+}