Wraps accounts.spotify.com login in a WKWebView so users can sign in
without opening the browser inspector to copy the sp_dc cookie. The
sheet uses a non-persistent data store, observes the cookie store, and
hands the captured value to the existing SpotifyAuthManager.validate
flow on a match.
Spotify's anti-bot blocks the WebView path for some accounts, so this
sits alongside (not replaces) the manual paste field, with an "Open in
Browser" escape hatch in the sheet toolbar.
Signed-off-by: Jis G Jacob <studiokeys@blissroms.org>
