feat(commons): add audit telemetry + pull message DTOs (#23)

src/ScadaLink.Commons/Messages/Integration/PullAuditEventsRequest.cs

@@ -0,0 +1,11 @@
+namespace ScadaLink.Commons.Messages.Integration;
+
+/// <summary>
+/// Audit Log (#23) periodic reconciliation pull request: central asks a site for
+/// audit events since the given UTC watermark, up to <paramref name="BatchSize"/>.
+/// Acts as the fallback when streaming telemetry is lost. See Component-AuditLog.md "Ingestion".
+/// </summary>
+public sealed record PullAuditEventsRequest(
+    string SourceSiteId,
+    DateTime SinceUtc,
+    int BatchSize);