feat: add React Native New Architecture support (RN 0.83+ / Expo SDK 55)

[mikemilla]

Summary

Adds compatibility with React Native's New Architecture, which is mandatory starting with RN 0.83+ (Expo SDK 55). The library now works in both bridge mode (old architecture) and bridgeless mode (New Architecture) using the interop layer with proper Turbo Module discovery.

Closes #35

Changes

Android

• build.gradle: Apply com.facebook.react plugin unconditionally (not gated behind newArchEnabled), so the library works when New Architecture is always enabled. Replaced the hardcoded com.facebook.react:react-android:0.73.7 dependency with a dynamic version (+) so the consumer's React Native version is used.
• CourierReactNativePackage.kt: Migrated from ReactPackage to TurboReactPackage, implementing getModule() and getReactModuleInfoProvider() for proper Turbo Module discovery in New Architecture.
• ReactNativeModule.kt: Replaced currentActivity as? ReactActivity with currentActivity as Activity?. In bridgeless mode, currentActivity may return a ComponentActivity rather than ReactActivity, making the old cast fail silently.
• CourierClientModule.kt: Updated putUserToken to use the safer activity reference.
• CourierSystemModule.kt: Updated registerPushNotificationClickedOnKilledState, requestNotificationPermission, and getNotificationPermissionStatus to use the safer activity reference.
• CourierPreferencesViewManager.kt: Added null safety for currentActivity casting to FragmentActivity.
• gradle.properties: Updated SDK versions (compileSdk/targetSdk 34, minSdk 24, Kotlin 1.9.24, NDK 26.1) for modern RN compatibility.

iOS

• courier-react-native.podspec: Cleaned up indentation in the New Architecture fallback block. The install_modules_dependencies helper (available in RN 0.71+) already handles both old and New Architecture setup automatically.
• CourierReactNativeDelegate.h: Changed #import "RCTAppDelegate.h" to #import <React/RCTAppDelegate.h> for proper module resolution.
• CourierReactNativeDelegate.m: Made bridgeless-mode safe by conditionally importing RCTBridge.h and using a string-based notification name for RCTBridgeWillReloadNotification (which doesn't exist in bridgeless mode).
• CourierReactNative-Bridging-Header.h: Added conditional RCTBridge.h import for backward compatibility.
• CourierSystemModule.swift: Added documentation comment about RCTBridgeWillReloadNotification behavior in bridgeless mode.

JavaScript

• Modules.tsx: Updated module lookup to try TurboModuleRegistry first (New Architecture) with automatic fallback to NativeModules (bridge mode / interop layer). This ensures the library works in both architectures.

Compatibility

• Old Architecture (RN < 0.83): Fully backward compatible. The interop layer and NativeModules fallback ensure existing apps continue to work.
• New Architecture (RN 0.83+): Works via the interop layer with TurboReactPackage discovery. Native modules are automatically wrapped as Turbo Modules, and view managers are wrapped for Fabric compatibility.

Testing

• All 125 unit tests pass
• TypeScript compilation passes (0 errors)
• ESLint passes (0 errors, only pre-existing warnings)