feat(sitecall-audit): carry + persist SourceNode end-to-end via cached telemetry

Site: site emitters of SiteCallOperational (ExternalSystemClient, the script-API
cached call path in ScriptRuntimeContext, CachedCallLifecycleBridge) inject
INodeIdentityProvider and stamp SourceNode = NodeName at construction.

OperationTrackingStore call site in CachedCallTelemetryForwarder now stamps
SourceNode too.

Central: SiteCallAuditRepository.UpsertAsync INSERT includes SourceNode in the
column list; conditional monotonic UPDATE uses
COALESCE(@SourceNode, SourceNode) so later packets cannot blank a previously-
stamped value. After this commit every SiteCalls row carries node-a/node-b in
SourceNode (subject to monotonic preservation).

src/ScadaLink.AuditLog/ServiceCollectionExtensions.cs

@@ -146,7 +146,14 @@ public static class ServiceCollectionExtensions
             new CachedCallTelemetryForwarder(
                 sp.GetRequiredService<IAuditWriter>(),
                 sp.GetService<ScadaLink.Commons.Interfaces.IOperationTrackingStore>(),
-                sp.GetRequiredService<ILogger<CachedCallTelemetryForwarder>>()));
+                sp.GetRequiredService<ILogger<CachedCallTelemetryForwarder>>(),
+                // SourceNode-stamping (Task 14): the local node identity is
+                // threaded through so RecordEnqueueAsync can stamp the
+                // tracking row's SourceNode column. GetService — central
+                // composition roots may not register the provider, in which
+                // case the forwarder degrades to a null SourceNode rather
+                // than failing the DI resolution.
+                sp.GetService<INodeIdentityProvider>()));
 
         // M3 Bundle F: bridge the store-and-forward retry-loop observer hook
         // to the cached-call forwarder so per-attempt + terminal telemetry
@@ -154,7 +161,17 @@ public static class ServiceCollectionExtensions
         // as the script-thread CachedSubmit row. Registered as a singleton
         // and also bound to ICachedCallLifecycleObserver so AddStoreAndForward
         // can resolve it through DI (Bundle F StoreAndForward wiring change).
-        services.AddSingleton<CachedCallLifecycleBridge>();
+        // SourceNode-stamping (Task 14): factory-resolved so the
+        // INodeIdentityProvider singleton can be threaded through — the
+        // bridge stamps SiteCallOperational.SourceNode from
+        // INodeIdentityProvider.NodeName on every cached-call lifecycle row.
+        // GetService (not GetRequiredService) — central composition roots may
+        // not register the provider, in which case the bridge degrades to a
+        // null SourceNode rather than failing the DI resolution.
+        services.AddSingleton<CachedCallLifecycleBridge>(sp => new CachedCallLifecycleBridge(
+            sp.GetRequiredService<ICachedCallTelemetryForwarder>(),
+            sp.GetRequiredService<ILogger<CachedCallLifecycleBridge>>(),
+            sp.GetService<INodeIdentityProvider>()));
         services.AddSingleton<ICachedCallLifecycleObserver>(
             sp => sp.GetRequiredService<CachedCallLifecycleBridge>());