feat(auditlog): site script-side emitters stamp ExecutionId

Move the per-script-execution Guid on ScriptRuntimeContext from
_auditCorrelationId to _executionId, and stamp it into the dedicated
AuditEvent.ExecutionId column on every script-side audit row:

- Sync ApiCall / DbWrite: ExecutionId set; CorrelationId reverts to
  null (a sync one-shot call has no operation lifecycle).
- Cached-call script-side rows (CachedSubmit, immediate-completion
  ApiCallCached + CachedResolve) and NotifySend: ExecutionId set;
  CorrelationId unchanged (per-operation TrackedOperationId /
  NotificationId).

Renames the threaded ctor param/field across ExternalSystemHelper,
DatabaseHelper, AuditingDbConnection and AuditingDbCommand, and threads
the id through NotifyHelper/NotifyTarget. The S&F retry-loop cached rows
(CachedCallLifecycleBridge) are out of scope here.

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

@@ -53,6 +53,12 @@ public class NotifySendAuditEmissionTests : TestKit, IAsyncLifetime, IDisposable
     private const string Subject = "Pump alarm";
     private const string Body = "Pump 3 tripped";
 
+    /// <summary>
+    /// Audit Log #23: a fixed per-execution id so the NotifySend test can
+    /// assert <see cref="AuditEvent.ExecutionId"/> against a known value.
+    /// </summary>
+    private static readonly Guid TestExecutionId = Guid.NewGuid();
+
     private readonly SqliteConnection _keepAlive;
     private readonly StoreAndForwardStorage _storage;
     private readonly StoreAndForwardService _saf;
@@ -102,6 +108,7 @@ public class NotifySendAuditEmissionTests : TestKit, IAsyncLifetime, IDisposable
             sourceScript,
             TimeSpan.FromSeconds(3),
             NullLogger.Instance,
+            TestExecutionId,
             auditWriter);
     }
 
@@ -214,12 +221,14 @@ public class NotifySendAuditEmissionTests : TestKit, IAsyncLifetime, IDisposable
 
         // NotificationId is minted as Guid.NewGuid().ToString("N") — the 32-char
         // hex form, which Guid.TryParse accepts. The audit row's CorrelationId
-        // must round-trip back to the same Guid value.
+        // must round-trip back to the same Guid value (the per-operation
+        // lifecycle id). ExecutionId carries the per-execution id instead.
         Assert.True(Guid.TryParse(notificationId, out var expected),
             $"NotificationId '{notificationId}' should be a parseable Guid");
         var evt = writer.Events[0];
         Assert.NotNull(evt.CorrelationId);
         Assert.Equal(expected, evt.CorrelationId);
+        Assert.Equal(TestExecutionId, evt.ExecutionId);
     }
 
     [Fact]