feat(siteruntime): ExternalSystem.CachedCall emits CachedSubmit telemetry (#23 M3)

Rework ScriptRuntimeContext.ExternalSystem.CachedCall to fit the M3
combined-telemetry model:

* Mints a fresh TrackedOperationId and emits one CachedSubmit packet
  via ICachedCallTelemetryForwarder BEFORE handing the call off — the
  SiteCalls row is materialised before the first delivery attempt so
  Tracking.Status(id) can observe a Submitted row even if immediate
  delivery resolves before the helper returns.
* Threads the TrackedOperationId into IExternalSystemClient.CachedCallAsync
  as a new optional parameter (and into IDatabaseGateway.CachedWriteAsync
  for the Database mirror set up here for E6). The gateway uses the id
  as the StoreAndForward messageId so the retry loop (Tasks E4/E5) can
  recover it from StoreAndForwardMessage.Id.
* Returns the TrackedOperationId rather than ExternalCallResult — the
  script's contract is now "get a tracking handle, observe outcome via
  Tracking.Status". Best-effort emission: a thrown forwarder is logged
  + swallowed; the original call still runs and the id is still returned.

DatabaseHelper gets the matching siteId / sourceScript / forwarder
fields and a parallel CachedSubmit emitter (Channel=DbOutbound) so Task
E6's Database.CachedWrite mirror plugs in without further runtime
wiring.

New ICachedCallTelemetryForwarder seam in Commons.Interfaces.Services
so SiteRuntime depends on Commons (existing arrow) rather than
ScadaLink.AuditLog (would have introduced a new dependency).

Bundle E task E3 (and helper-shape work for E6).

src/ScadaLink.Commons/Interfaces/Services/IDatabaseGateway.cs

@@ -1,4 +1,5 @@
 using System.Data.Common;
+using ScadaLink.Commons.Types;
 
 namespace ScadaLink.Commons.Interfaces.Services;
 
@@ -20,10 +21,19 @@ public interface IDatabaseGateway
     /// <summary>
     /// Submits a SQL write to the store-and-forward engine for reliable delivery.
     /// </summary>
+    /// <param name="trackedOperationId">
+    /// Audit Log #23 (M3): caller-supplied tracking id used as the
+    /// store-and-forward message id so the S&amp;F retry loop can read it
+    /// back via <c>StoreAndForwardMessage.Id</c> and emit per-attempt /
+    /// terminal cached-write telemetry under the same id. Defaults to
+    /// <c>null</c> — when omitted the S&amp;F engine mints a fresh GUID and no
+    /// M3 telemetry is correlated (pre-M3 caller behaviour).
+    /// </param>
     Task CachedWriteAsync(
         string connectionName,
         string sql,
         IReadOnlyDictionary<string, object?>? parameters = null,
         string? originInstanceName = null,
-        CancellationToken cancellationToken = default);
+        CancellationToken cancellationToken = default,
+        TrackedOperationId? trackedOperationId = null);
 }