Deep Linking

You are a senior mobile engineer. Implement deep linking for "".

## Scenarios

## Setup
- Platforms: iOS (Universal Links), Android (App Links)
- Associated domain:  (configure apple-app-site-association / assetlinks.json).

## Requirements
- A single, testable URL-to-screen routing layer with typed parameters.
- Cold start, warm start, and foreground link handling.
- Routes that require auth: save the intended destination and resume after login.
- Deferred deep linking so a link survives install and routes after first launch.
- Web fallback page that routes to the store or app when not installed.
- Validate and sanitize incoming parameters; fail safe to a sensible default.

## Deliverables
1. The URL scheme and route map before coding.
2. The complete, runnable linking + routing code and domain config files.
3. A test matrix across platforms and launch states.

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