fix(ios): add missing Assets.xcassets with AppIcon for test app

Created missing asset catalog required by Xcode build:

Assets.xcassets:
- Created asset catalog directory structure
- Added Contents.json with standard Xcode format
- Added AppIcon.appiconset with minimal icon configuration

AppIcon.appiconset:
- Minimal icon set configuration for iOS
- Universal platform support
- 1024x1024 size placeholder (actual icons can be added later)

Fixes:
- Build error: 'None of the input catalogs contained a matching app icon set named AppIcon'
- Build error: 'Failed to read file attributes for Assets.xcassets'
- Xcode project expects this asset catalog for app icons

Result: Build should now complete successfully

test-apps/ios-test-app/App/App/Assets.xcassets/AppIcon.appiconset/Contents.json

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

test-apps/ios-test-app/App/App/Assets.xcassets/Contents.json

@@ -0,0 +1,7 @@
+{
+  "info" : {
+    "version" : 1,
+    "author" : "xcode"
+  }
+}
+