Stabilizza live YouTube/RTMP e fix crash rotazione mobile.

Pipeline YouTube con relay, overlay e publisher sync lato backend; fix GL pauseGlDuringRotation su Android per evitare crash in rotazione durante lo streaming Flutter.

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/app/jobs/youtube_relay_stop_job.rb

@@ -0,0 +1,10 @@
+class YoutubeRelayStopJob < ApplicationJob
+  queue_as :default
+
+  def perform(session_id)
+    session = StreamSession.find_by(id: session_id)
+    return unless session
+
+    Streams::YoutubeRelay.stop_on_worker!(session) if Streams::YoutubeRelay.worker?
+  end
+end