chore(communication): low-severity cleanup — eviction counting, shared ingest timeout, split app heartbeat interval, doc notes

src/ZB.MOM.WW.ScadaBridge.Communication/Actors/StreamRelayActor.cs

@@ -104,9 +104,13 @@ public class StreamRelayActor : ReceiveActor
 
     private void WriteToChannel(SiteStreamEvent protoEvent)
     {
+        // TryWrite on a DropOldest bounded channel never returns false for a "full"
+        // channel — eviction of the oldest item is what happens instead, and it is
+        // counted by the channel's itemDropped callback (SiteStreamGrpcServer). This
+        // branch therefore guards only a completed/closed channel, not backpressure.
         if (!_channelWriter.TryWrite(protoEvent))
         {
-            _log.Warning("Channel full, dropping event for correlation {0}", _correlationId);
+            _log.Debug("Channel closed, dropping event for correlation {0}", _correlationId);
         }
     }