update readme

Author: piotr-iohk

README.md

@@ -50,7 +50,7 @@ test/
 
 ### 🧱 Build apps locally (Android/iOS)
 
-If you have `bitkit-e2e-tests`, `bitkit-android`, and `bitkit-ios` checked out in the same parent directory, you can use the helper scripts to build local artifacts. The outputs land in `./aut` and are ready to be tested.
+If you have `bitkit-e2e-tests`, `bitkit-android`, and `bitkit-ios` checked out in the same parent directory, you can use the helper scripts to build local artifacts (local Electrum by default). The outputs land in `./aut` and are ready to be tested.
 
 ```bash
 # Android (builds ../bitkit-android and copies APK to ./aut/bitkit_e2e.apk)
@@ -60,14 +60,16 @@ If you have `bitkit-e2e-tests`, `bitkit-android`, and `bitkit-ios` checked out i
 ./scripts/build-ios-sim.sh
 ```
 
-Optional Android backend selection:
+Optional backend selection (`BACKEND=local` is default and can be omitted):
 
 ```bash
-# local Electrum (default)
-./scripts/build-android-apk.sh
-
-# regtest Electrum (network)
+# Android
+BACKEND=local ./scripts/build-android-apk.sh
 BACKEND=regtest ./scripts/build-android-apk.sh
+
+# iOS
+BACKEND=local ./scripts/build-ios-sim.sh
+BACKEND=regtest ./scripts/build-ios-sim.sh
 ```
 
 ---