Without the EXPO_PUBLIC_ prefix, Expo's bundler strips these vars from
production builds, leaving them undefined and breaking Pusher connections
in EAS/TestFlight builds.

- Change app display name from 'shatter-mobile' to 'Shatter'
- Disable expo-camera microphone/audio permissions; only QR scanning
  is used, so requesting mic access risks App Store rejection

Camera is only used for QR scanning; audio recording is not needed.

Mobile

Backend: encode 'platform' (mobile|web) into the signed state JWT in
linkedinAuth and linkedinLink. In linkedinCallback, verify state first
and resolve the redirect target from the platform claim — mobile gets
shattermobile://auth, web keeps the existing FRONTEND_URL flow. All
success/error redirects in the callback use the resolved target so the
mobile app receives the auth code (or error) via deep link.

Mobile: switch LinkedIn login from openBrowserAsync to
openAuthSessionAsync so the in-app browser closes on the deep-link
return and the redirect URL is captured in JS. Extract a shared
loginWithLinkedIn helper that handles the full flow (open browser,
parse code, exchange, fetch user) and call it from both LoginForm and
SignupForm with proper loading/error state.

EAS/TestFlight setup and LinkedIn mobile deep-link

React Native's built-in URL constructor does not robustly handle custom
schemes like shattermobile://, causing the deep-link callback URL to
fail to parse and login to silently fail. Switch to Linking.parse from
expo-linking, which is purpose-built for custom-scheme URLs and is
already a project dependency.

Parse LinkedIn deep-link with expo-linking