Fix YouTube in attesa: audio AAC di riserva, retry attivazione broadcast

Il relay verso YouTube ora gestisce _air senza traccia audio, ritenta
activate_broadcast finché l'ingest è active e riduce la finestra
scheduledStartTime a ~20s.

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

backend/app/services/youtube/broadcast_service.rb

@@ -51,31 +51,38 @@ module Youtube
     end
 
     # Porta in onda appena c’è ingest su YouTube (non attendere scheduledStartTime).
+    # @return [Symbol] :live, :waiting_ingest, :transitioned, :skipped
     def activate_broadcast!(broadcast_id)
-      return if broadcast_id.blank?
-      return if @credential.blank? || missing_oauth_config?
+      return :skipped if broadcast_id.blank?
+      return :skipped if @credential.blank? || missing_oauth_config?
 
       client = authorized_client
       item = client.list_live_broadcasts("status,contentDetails", id: broadcast_id).items&.first
-      return unless item
+      return :skipped unless item
 
       status = item.status.life_cycle_status.to_s
-      return if status == "live"
+      return :live if status == "live"
 
       stream_id = item.content_details&.bound_stream_id
       if stream_id.present?
         stream = client.list_live_streams("status", id: stream_id).items&.first
-        return if stream&.status&.stream_status != "active"
+        stream_status = stream&.status&.stream_status.to_s
+        return :waiting_ingest unless stream_status == "active"
       end
 
       if %w[ready created].include?(status)
         client.transition_live_broadcast("testing", broadcast_id, "id,status")
         status = "testing"
       end
-      client.transition_live_broadcast("live", broadcast_id, "id,status") if status == "testing"
+      if status == "testing"
+        client.transition_live_broadcast("live", broadcast_id, "id,status")
+        return :transitioned
+      end
+
+      :skipped
     rescue Google::Apis::Error => e
       Rails.logger.warn("[Youtube::BroadcastService] activate #{broadcast_id}: #{e.message}")
-      nil
+      :skipped
     end
 
     def complete_broadcast!(broadcast_id)
@@ -131,7 +138,7 @@ module Youtube
     # YouTube richiede scheduledStartTime nel futuro; per «vai subito» usiamo ~1 min (auto_start al RTMP).
     def normalize_scheduled_start_time(scheduled_at)
       now = Time.current.utc
-      minimum = now + 90.seconds
+      minimum = now + 20.seconds
       maximum = now + 7.days
 
       candidate =