feat(siteeventlog): emit store_and_forward + notification events (M1.7)

StoreAndForwardService gains an optional ISiteEventLogger? ctor param (default
null so the many direct-construction tests still compile) and, when wired,
mirrors its own buffer/retry/park activity onto site operational events via the
existing OnActivity hook (which already isolates a throwing subscriber, so a
failing event log can never be misclassified as a transient delivery failure):

- store_and_forward (ExternalSystem / CachedDbWrite): queued/retried/delivered/
  parked. Warning on buffer/retry, Error on park, Info on retry-recovery; an
  immediate-success delivery is the hot path and is not logged.
- notification (the site forward-to-central path): logged ONLY on forward
  FAILURE (buffered after the immediate forward threw) and on park, per the
  Component-SiteEventLogging spec — routine enqueue and forward-success are
  deliberately not logged (central's Notifications table is the audit record).

Wired through AddStoreAndForward (resolves ISiteEventLogger optionally from DI);
StoreAndForward project now references SiteEventLogging (acyclic: SiteEventLogging
references only Commons). Also documents the 'notification' category on the
ISiteEventLogger.LogEventAsync eventType param (folds in M1.8 doc fix).

src/ZB.MOM.WW.ScadaBridge.SiteEventLogging/ISiteEventLogger.cs

@@ -11,7 +11,7 @@ public interface ISiteEventLogger
     /// <see cref="Task"/> completes once the event is durably persisted and faults if
     /// the write fails, so callers that <c>await</c> it observe success or failure.
     /// </summary>
-    /// <param name="eventType">Category: script, alarm, deployment, connection, store_and_forward, instance_lifecycle</param>
+    /// <param name="eventType">Category: script, alarm, deployment, connection, store_and_forward, instance_lifecycle, notification</param>
     /// <param name="severity">Info, Warning, or Error</param>
     /// <param name="instanceId">Optional instance ID associated with the event</param>
     /// <param name="source">Source identifier, e.g., "ScriptActor:MonitorSpeed"</param>