port mobile app to React Native: search, miniplayer, icons, sign-in copy
This covers the major threads: the full Search screen rewrite (correct
endpoint, flat hits shape, Feather icon), MiniPlayer with Rockbox WebSocket
controls and playback lock, app icon replaced with the Rocksky favicon, and
sign-in copy aligned with web/web-mobile (Handle label, atproto signup text,
selfhosted.social OAuth flow).