feat(auditlog): thread ParentExecutionId 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. The ExecutionId rollout (Task 4) already threaded ExecutionId
and SourceScript through this path; ParentExecutionId — the spawning
inbound-API request's ExecutionId — was not, so those retry-loop rows had
ParentExecutionId = null even for an inbound-API-routed run.

Thread it additively as a sibling at every carry point ExecutionId passes
through:

- StoreAndForwardMessage gains ParentExecutionId (Guid?).
- StoreAndForwardStorage adds a nullable parent_execution_id column via the
  same idempotent PRAGMA-probed ALTER TABLE migration; rows persisted by an
  older build read back null (back-compat). The defensive Guid.TryParse read
  helper (ParseExecutionId) is renamed ParseGuidColumn and reused for both
  columns so a corrupt value cannot abort the retry sweep.
- StoreAndForwardService.EnqueueAsync gains an optional parentExecutionId
  param, stamped onto the buffered message and surfaced on the
  CachedCallAttemptContext built in the retry loop.
- CachedCallAttemptContext gains ParentExecutionId.
- CachedCallLifecycleBridge.BuildPacket sets AuditEvent.ParentExecutionId
  from the context, beside the existing ExecutionId.
- IExternalSystemClient.CachedCallAsync / IDatabaseGateway.CachedWriteAsync
  gain an optional parentExecutionId param; ScriptRuntimeContext's CachedCall
  / CachedWrite helpers pass _parentExecutionId.

All threading is additive — ParentExecutionId is Guid? everywhere, null for
non-routed runs, and old buffered S&F rows still deserialize with the new
field null.

src/ScadaLink.StoreAndForward/StoreAndForwardService.cs

@@ -187,6 +187,14 @@ public class StoreAndForwardService
     /// so the retry-loop audit rows carry the same provenance the script-side
     /// cached rows do. <c>null</c> when not known.
     /// </param>
+    /// <param name="parentExecutionId">
+    /// Audit Log #23 (ParentExecutionId Task 6): the <c>ExecutionId</c> of the
+    /// inbound-API request that spawned the originating script execution.
+    /// Threaded onto the buffered row alongside <paramref name="executionId"/>
+    /// so the retry-loop cached-call audit rows carry it. <c>null</c> for a
+    /// non-routed run and for callers (notifications, pre-Task-6 callers) that
+    /// do not supply one.
+    /// </param>
     public async Task<StoreAndForwardResult> EnqueueAsync(
         StoreAndForwardCategory category,
         string target,
@@ -197,7 +205,8 @@ public class StoreAndForwardService
         bool attemptImmediateDelivery = true,
         string? messageId = null,
         Guid? executionId = null,
-        string? sourceScript = null)
+        string? sourceScript = null,
+        Guid? parentExecutionId = null)
     {
         var message = new StoreAndForwardMessage
         {
@@ -212,7 +221,8 @@ public class StoreAndForwardService
             Status = StoreAndForwardMessageStatus.Pending,
             OriginInstanceName = originInstanceName,
             ExecutionId = executionId,
-            SourceScript = sourceScript
+            SourceScript = sourceScript,
+            ParentExecutionId = parentExecutionId
         };
 
         // Attempt immediate delivery — unless the caller has already made a
@@ -515,7 +525,13 @@ public class StoreAndForwardService
                 // stamp the retry-loop cached audit rows. Null on rows buffered
                 // before Task 4 (back-compat).
                 ExecutionId: message.ExecutionId,
-                SourceScript: message.SourceScript);
+                SourceScript: message.SourceScript,
+                // Audit Log #23 (ParentExecutionId Task 6): the buffered
+                // message also carries the spawning inbound-API request's
+                // ExecutionId; surface it so the bridge stamps it onto the
+                // retry-loop cached rows. Null for a non-routed run and on
+                // rows buffered before Task 6 (back-compat).
+                ParentExecutionId: message.ParentExecutionId);
         }
         catch (Exception buildEx)
         {