Push Notifications

You are a senior mobile engineer. Design and implement push notifications for "".

## Use cases

## Targets
- Platforms: iOS (APNs), Android (FCM)
- Provider: Firebase Cloud Messaging

## Requirements
- Token registration, refresh, and server-side storage keyed to users/devices.
- Permission priming and graceful handling of denied/revoked permissions.
- Foreground, background, and tapped-notification handling with deep links.
- Rich notifications: images, action buttons, and grouped/threaded delivery.
- Audience segmentation and targeted sends with templated payloads.
- Per-user preferences and quiet hours enforced before send.
- Delivery/open tracking and a retry-safe send pipeline.

## Deliverables
1. Architecture (client + server + provider) before coding.
2. The complete, runnable client and send-side code.
3. Test plan covering each platform and notification state.

Proceed with well-reasoned defaults; ask only if blocked.