fix(ios): ensure capacitor-assets output dirs exist on fresh clones

Gitignored AppIcon.appiconset and Splash.imageset are absent after clone,
which made `capacitor-assets generate --ios` fail (missing paths and
Contents.json). Add ensure_ios_capacitor_asset_directories in common.sh
to mkdir and seed minimal Contents.json when needed; call it from
build-ios.sh before asset generation and from the build:native npm script.
Document the behavior in ios/.gitignore.

scripts/build-ios.sh

@@ -413,6 +413,7 @@ fi
 # Handle assets-only mode
 if [ "$ASSETS_ONLY" = true ]; then
     log_info "Assets-only mode: generating assets"
+    ensure_ios_capacitor_asset_directories
     safe_execute "Generating assets" "npx capacitor-assets generate --ios" || exit 7
     log_success "Assets generation completed successfully!"
     exit 0
@@ -562,6 +563,7 @@ safe_execute "Installing CocoaPods dependencies" "run_pod_install_with_workaroun
 safe_execute "Syncing with Capacitor" "run_cap_sync_with_workaround" || exit 6
 
 # Step 7: Generate assets
+ensure_ios_capacitor_asset_directories
 safe_execute "Generating assets" "npx capacitor-assets generate --ios" || exit 7
 
 # Step 8: Build iOS app