Redirects for deprecated routes handled gracefully

Renamed or retired screens leave a long tail of deep links in the wild — old emails, shared URLs, indexed Google results, push-notification payloads from older app versions. Without aliases or a fallback handler, those links either crash the app or dump users on an unhandled route, breaking referral traffic and surfacing as negative store reviews. Reference-integrity on deep links is the mobile equivalent of HTTP 301 redirects on the web.

Add deprecated-route aliases and a fallback handler to the linking config so old URLs resolve cleanly. In src/navigation/linking.ts:

export const linking = {
  prefixes: ['myapp://', 'https://myapp.com'],
  config: {
    screens: {
      ProductDetail: 'product/:id',
      ProductView: 'product/:id', // deprecated alias
    },
  },
  getStateFromPath: (path, options) => {
    // fall through to Home if unresolved
    return getStateFromPath(path, options) ?? { routes: [{ name: 'Home' }] }
  },
}