Adds an opt-in native HLS video player (iOS-only, off by default) that
uses AVPlayerViewController for true automatic picture-in-picture on
swipe-home, replacing the WebView-based player when enabled.
Key changes:
- GQL API client for fetching playback access tokens and building HLS URLs
- NativeVideoStore (MobX) managing player lifecycle, quality selection, PiP
- VideoPlayerInterface abstraction so both stores drive the same overlay
- Settings toggle gated on iOS with "Native player (experimental)" label
- Auth token fallback: tries authenticated GQL for ad-free, falls back to
anonymous if rejected (app OAuth token != web Client-ID token)
- Scoped UnauthorizedInterceptor to Helix/OAuth URLs only
- iOS Info.plist background audio mode for PiP audio continuity
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
