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

src/ZB.MOM.WW.ScadaBridge.Communication/CommunicationOptions.cs

@@ -56,6 +56,14 @@ public class CommunicationOptions
     /// <summary>Akka.Remote transport heartbeat interval.</summary>
     public TimeSpan TransportHeartbeatInterval { get; set; } = TimeSpan.FromSeconds(5);
 
+    /// <summary>
+    /// Application-level site→central heartbeat cadence. Distinct from
+    /// <see cref="TransportHeartbeatInterval"/> (the Akka.Remote failure-detector
+    /// setting) — tuning the transport FD must not silently retune the health
+    /// heartbeat. Default equals the old effective value (5s) — no behavior change.
+    /// </summary>
+    public TimeSpan ApplicationHeartbeatInterval { get; set; } = TimeSpan.FromSeconds(5);
+
     /// <summary>Akka.Remote transport failure detection threshold.</summary>
     public TimeSpan TransportFailureThreshold { get; set; } = TimeSpan.FromSeconds(15);