pushEnabled property

Fetch Remote Config at startup (and on foreground). Read values via nexus.remoteConfig.getString(...) etc. Default false (billed per fetch — opt in). Set in-app fallbacks with remoteConfigDefaults. Turn-key push notifications. When true, the SDK requests permission, obtains the device's FCM token, registers it with Nexus, re-registers on refresh, and reports notification opens — all automatically. You only need the platform Firebase config (google-services.json / GoogleService-Info.plist). Default false.