The Sources -> Edit Source -> Proxy toggle now renders for Yattee
Server entries (supportsVideoProxying gains .yatteeServer). When the
toggle is on, playback fetches go through
videoWithProxyStreamsAndCaptionsAndStoryboards with mode .relay, so
the server returns signed /proxy/relay URLs (byte-relay, supports
HTTP Range, no on-disk caching). Downloads keep going through mode
.download so the server-side /proxy/fast/ flow continues to cache
files for repeat use.
InvidiousAPI.proxyStreamsIfNeeded early-returns for .yatteeServer
since proxying is now done at fetch time via ?proxy=true rather than
client-side host rewriting.