feat(demo): [SDK-4217] add Live Activities demp example

[fadi-george]

Description

One Line Summary

Add Live Activities support to the React Native demo app with an iOS delivery order tracking widget.

Details

Motivation

The demo app was missing Live Activities support, which is needed to demonstrate and test the OneSignal Live Activities SDK features (push-to-start, push-to-update) from the React Native wrapper.

Scope

• Demo app: Adds a LiveActivitySection (iOS only) with start, update (cycle through order statuses), stop updating, and end buttons
• iOS widget: Adds OneSignalWidgetLiveActivity widget extension with Lock Screen banner, Dynamic Island, and animated delivery progress bar displaying order number, status, message, and ETA
• API integration: Update and end operations go through the OneSignal REST API using ONESIGNAL_API_KEY from .env (via react-native-dotenv); start and stop-updating use the SDK directly
• Cleanup: Remove duplicate plugins key in babel.config.js and duplicate .env entry in .gitignore
• No SDK changes

Testing

Unit testing

All 244 existing tests pass via vp test. No new unit tests needed — changes are limited to the demo app UI and API calls.

Manual testing

• Configure .env with a valid ONESIGNAL_API_KEY and verify update/end buttons are enabled
• Run without .env and verify update/end buttons are disabled
• Start a live activity and verify the Lock Screen banner and Dynamic Island render correctly
• Cycle through all order statuses (preparing → on the way → delivered) and verify the widget updates
• End the live activity and verify it dismisses
• Verify Live Activities section only appears on iOS

Affected code checklist

• Notifications
  • Display
• Outcomes
• Sessions
• In-App Messaging
• REST API requests
• Public API changes

Checklist

Overview

• I have filled out all REQUIRED sections above
• PR does one thing
• Any Public API changes are explained in the PR details and conform to existing APIs

Testing

• I have included test coverage for these changes, or explained why they are not needed
• All automated tests pass, or I explained why that is not possible
• I have personally tested this on my device, or explained why that is not possible

Final pass

• Code is as readable as possible.
• I have reviewed this PR myself, ensuring it meets each checklist item