feat(apple): adopt Icon Composer app icon

Replace the legacy AppIcon.appiconset with an Icon Composer AppIcon.icon
bundle in the target's resources. ASSETCATALOG_COMPILER_APPICON_NAME already
points at "AppIcon"; the .icon back-deploys to the iOS 18.2 target.

apple/VniDrop/Resources/Assets.xcassets/AppIcon.appiconset/Contents.json

@@ -1,7 +0,0 @@
-{
-  "images" : [
-    { "idiom" : "universal", "platform" : "ios", "size" : "1024x1024", "filename" : "app-icon.png" },
-    { "idiom" : "mac", "scale" : "2x", "size" : "512x512", "filename" : "app-icon.png" }
-  ],
-  "info" : { "author" : "xcode", "version" : 1 }
-}