Add lifecycle callbacks for iOS and tvOS

[olipetrovic]

Add lifecycle callbacks for iOS and tvOS

iOS and tvOS suspend the process while the app is in the background, which freezes the delay-based auto-refresh timer. Without lifecycle callbacks the timer can sleep through the access token's expiry, leaving every request with an expired JWT (PostgREST 401 PGRST303) after the app returns to the foreground - until the user signs out and back in. Hit this in production: the edge logs for the incident show a burst of 401s on every data request and not a single grant_type=refresh_token call.

What this does

Mirrors the Android implementation via NSNotificationCenter:

• On UIApplicationDidEnterBackgroundNotification: cancel auto refresh and set the status to Initializing, as Android's onStop does.
• On UIApplicationWillEnterForegroundNotification: re-load the session from storage, which runs the existing threshold check - refreshing immediately if the token went stale while suspended, or re-arming the timer with the correct remaining time if not.

Gated behind the existing enableLifecycleCallbacks config flag (its doc now says Android, iOS and tvOS).

Structure

The appleMain setupPlatform actual now delegates to a per-family setupApplePlatform expect:

• a new uikit intermediate source set (iOS + tvOS, added to the hierarchy in Auth/build.gradle.kts) holds the observer registration;
• macOS keeps the previous initDone()-only behavior - processes are not suspended there, so the timer keeps running;
• watchOS also keeps the previous behavior for now - it does suspend apps, but its lifecycle notifications live in WatchKit (WKApplication), not UIKit, so it would need its own implementation.

Notes

• No behavior change when enableLifecycleCallbacks = false.
• Verified: :auth-kt:compileKotlinIosArm64, compileKotlinIosSimulatorArm64, compileKotlinTvosArm64, compileKotlinWatchosArm64, compileKotlinMacosArm64, compileKotlinJvm, allMetadataJar.