Aggiunge overlay server-side burn-in e stabilizza diretta live.

Tabellone, badge e brand sono ricodificati nel flusso _air via OverlayRelay;
sync punteggio HTTP, volume condiviso rails/sidekiq, qualità 720p migliorata
e badge CONNECTING in ripresa da pausa.

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

backend/app/jobs/overlay_refresh_job.rb

@@ -0,0 +1,31 @@
+class OverlayRefreshJob < ApplicationJob
+  queue_as :default
+
+  INTERVAL = 2.seconds
+  REDIS_CHAIN_KEY = "overlay_refresh:chain:%s"
+
+  def self.schedule_chain(session_id)
+    redis.set(format(REDIS_CHAIN_KEY, session_id), "1", ex: 48.hours.to_i)
+    set(wait: INTERVAL).perform_later(session_id)
+  end
+
+  def self.cancel_chain(session_id)
+    redis.del(format(REDIS_CHAIN_KEY, session_id))
+  end
+
+  def self.redis
+    @redis ||= Redis.new(url: ENV.fetch("REDIS_URL", "redis://localhost:6379/0"))
+  end
+
+  def perform(session_id)
+    return unless self.class.redis.get(format(REDIS_CHAIN_KEY, session_id))
+
+    session = StreamSession.find_by(id: session_id)
+    return self.class.cancel_chain(session_id) unless session
+    return self.class.cancel_chain(session_id) if session.terminal?
+    return self.class.cancel_chain(session_id) unless Streams::OverlayRelay.running?(session_id)
+
+    Streams::Overlay::Refresh.call(session)
+    self.class.set(wait: INTERVAL).perform_later(session_id)
+  end
+end