feat(auditlog): thread ExecutionId through S&F for retry-loop cached rows

The store-and-forward retry loop emits the per-attempt and terminal cached
audit rows (ApiCallCached/DbWriteCached Attempted, CachedResolve) via
CachedCallLifecycleBridge from a CachedCallAttemptContext, not from the
script context. ExecutionId (and SourceScript) were not threaded through the
S&F buffer, so those rows had ExecutionId = null and SourceScript = null.

Thread both, additively, from the cached-call enqueue path:

- StoreAndForwardMessage gains ExecutionId (Guid?) / SourceScript (string?).
- StoreAndForwardStorage adds nullable execution_id / source_script columns
  via an idempotent PRAGMA-probed ALTER TABLE migration; rows persisted by
  an older build read back null (back-compat).
- StoreAndForwardService.EnqueueAsync gains optional executionId /
  sourceScript params, stamped onto the buffered message and surfaced on the
  CachedCallAttemptContext built in the retry loop.
- CachedCallAttemptContext gains ExecutionId / SourceScript.
- CachedCallLifecycleBridge.BuildPacket sets AuditEvent.ExecutionId and
  AuditEvent.SourceScript from the context (replacing the hard-coded
  SourceScript = null and its now-stale comment).
- IExternalSystemClient.CachedCallAsync / IDatabaseGateway.CachedWriteAsync
  gain optional executionId / sourceScript params; ScriptRuntimeContext's
  CachedCall / CachedWrite helpers pass _executionId / _sourceScript.

Script-side cached rows (CachedSubmit, immediate Attempted+Resolve) are
unchanged. All threading is additive — old buffered S&F rows still
deserialize and process with the new fields null.

tests/ScadaLink.SiteRuntime.Tests/Scripts/DatabaseCachedWriteEmissionTests.cs

@@ -72,7 +72,8 @@ public class DatabaseCachedWriteEmissionTests
                 It.IsAny<IReadOnlyDictionary<string, object?>?>(),
                 InstanceName,
                 It.IsAny<CancellationToken>(),
-                It.IsAny<TrackedOperationId?>()))
+                It.IsAny<TrackedOperationId?>(),
+                It.IsAny<Guid?>(), It.IsAny<string?>()))
             .Returns(Task.CompletedTask);
         var forwarder = new CapturingForwarder();
 
@@ -110,7 +111,8 @@ public class DatabaseCachedWriteEmissionTests
                 It.IsAny<IReadOnlyDictionary<string, object?>?>(),
                 It.IsAny<string?>(),
                 It.IsAny<CancellationToken>(),
-                It.IsAny<TrackedOperationId?>()))
+                It.IsAny<TrackedOperationId?>(),
+                It.IsAny<Guid?>(), It.IsAny<string?>()))
             .Returns(Task.CompletedTask);
         var forwarder = new CapturingForwarder();
 
@@ -134,7 +136,8 @@ public class DatabaseCachedWriteEmissionTests
                 It.IsAny<IReadOnlyDictionary<string, object?>?>(),
                 It.IsAny<string?>(),
                 It.IsAny<CancellationToken>(),
-                It.IsAny<TrackedOperationId?>()))
+                It.IsAny<TrackedOperationId?>(),
+                It.IsAny<Guid?>(), It.IsAny<string?>()))
             .Returns(Task.CompletedTask);
         var forwarder = new CapturingForwarder();
 
@@ -147,7 +150,8 @@ public class DatabaseCachedWriteEmissionTests
             It.IsAny<IReadOnlyDictionary<string, object?>?>(),
             InstanceName,
             It.IsAny<CancellationToken>(),
-            trackedId),
+            trackedId,
+            It.IsAny<Guid?>(), It.IsAny<string?>()),
             Times.Once);
     }
 
@@ -161,7 +165,8 @@ public class DatabaseCachedWriteEmissionTests
                 It.IsAny<IReadOnlyDictionary<string, object?>?>(),
                 It.IsAny<string?>(),
                 It.IsAny<CancellationToken>(),
-                It.IsAny<TrackedOperationId?>()))
+                It.IsAny<TrackedOperationId?>(),
+                It.IsAny<Guid?>(), It.IsAny<string?>()))
             .Returns(Task.CompletedTask);
         var forwarder = new CapturingForwarder
         {
@@ -177,7 +182,8 @@ public class DatabaseCachedWriteEmissionTests
             It.IsAny<IReadOnlyDictionary<string, object?>?>(),
             InstanceName,
             It.IsAny<CancellationToken>(),
-            trackedId),
+            trackedId,
+            It.IsAny<Guid?>(), It.IsAny<string?>()),
             Times.Once);
     }
 }