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.StoreAndForward/ServiceCollectionExtensions.cs

@@ -2,6 +2,7 @@ using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Logging;
 using Microsoft.Extensions.Options;
 using ZB.MOM.WW.ScadaBridge.Commons.Interfaces.Services;
+using ZB.MOM.WW.ScadaBridge.SiteEventLogging;
 
 namespace ZB.MOM.WW.ScadaBridge.StoreAndForward;
 
@@ -49,13 +50,19 @@ public static class ServiceCollectionExtensions
             // observable in the central audit log instead of producing a
             // silent empty-string SourceSite.
             var siteId = siteContext?.SiteId ?? string.Empty;
+            // M1.7: optional site operational-event log. Resolved through
+            // GetService so a host (or test) that has not called
+            // AddSiteEventLogging simply gets null and the S&F activity stays
+            // a no-op for site-event purposes.
+            var siteEventLogger = sp.GetService<ISiteEventLogger>();
             return new StoreAndForwardService(
                 storage,
                 options,
                 logger,
                 replication,
                 cachedCallObserver,
-                siteId);
+                siteId,
+                siteEventLogger);
         });
 
         services.AddSingleton<ReplicationService>(sp =>