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.

src/ScadaLink.StoreAndForward/StoreAndForwardService.cs

@@ -175,6 +175,18 @@ public class StoreAndForwardService
     /// it is the buffered row's <see cref="StoreAndForwardMessage.Id"/>, it is carried
     /// inside the payload, and it is the id the forwarder submits to central.
     /// </param>
+    /// <param name="executionId">
+    /// Audit Log #23 (ExecutionId Task 4): the originating script execution's
+    /// per-run correlation id. Threaded onto the buffered row so the retry-loop
+    /// cached-call audit rows carry it. <c>null</c> for callers (notifications,
+    /// pre-Task-4 callers) that do not supply one.
+    /// </param>
+    /// <param name="sourceScript">
+    /// Audit Log #23 (ExecutionId Task 4): the originating script identifier,
+    /// threaded onto the buffered row alongside <paramref name="executionId"/>
+    /// so the retry-loop audit rows carry the same provenance the script-side
+    /// cached rows do. <c>null</c> when not known.
+    /// </param>
     public async Task<StoreAndForwardResult> EnqueueAsync(
         StoreAndForwardCategory category,
         string target,
@@ -183,7 +195,9 @@ public class StoreAndForwardService
         int? maxRetries = null,
         TimeSpan? retryInterval = null,
         bool attemptImmediateDelivery = true,
-        string? messageId = null)
+        string? messageId = null,
+        Guid? executionId = null,
+        string? sourceScript = null)
     {
         var message = new StoreAndForwardMessage
         {
@@ -196,7 +210,9 @@ public class StoreAndForwardService
             RetryIntervalMs = (long)(retryInterval ?? _options.DefaultRetryInterval).TotalMilliseconds,
             CreatedAt = DateTimeOffset.UtcNow,
             Status = StoreAndForwardMessageStatus.Pending,
-            OriginInstanceName = originInstanceName
+            OriginInstanceName = originInstanceName,
+            ExecutionId = executionId,
+            SourceScript = sourceScript
         };
 
         // Attempt immediate delivery — unless the caller has already made a
@@ -492,7 +508,14 @@ public class StoreAndForwardService
                 CreatedAtUtc: message.CreatedAt.UtcDateTime,
                 OccurredAtUtc: DateTime.SpecifyKind(occurredAtUtc, DateTimeKind.Utc),
                 DurationMs: durationMs,
-                SourceInstanceId: message.OriginInstanceName);
+                SourceInstanceId: message.OriginInstanceName,
+                // Audit Log #23 (ExecutionId Task 4): the buffered message
+                // carries the originating script execution's ExecutionId +
+                // SourceScript; surface them on the context so the bridge can
+                // stamp the retry-loop cached audit rows. Null on rows buffered
+                // before Task 4 (back-compat).
+                ExecutionId: message.ExecutionId,
+                SourceScript: message.SourceScript);
         }
         catch (Exception buildEx)
         {