feat(auditlog): extend ISiteStreamAuditClient with IngestCachedTelemetryAsync (#23 M3)

Add the second site→central RPC seam alongside the existing M2
IngestAuditEventsAsync. The Bundle D proto already lit up
IngestCachedTelemetry (CachedTelemetryBatch / IngestAck) so this commit
just plumbs the client-side abstraction:

* ISiteStreamAuditClient gains IngestCachedTelemetryAsync(batch, ct).
* NoOpSiteStreamAuditClient implements it returning an empty IngestAck
  (same shape as M2 — production gRPC client lands in M6).
* SyncCallEmissionEndToEndTests' DirectActorSiteStreamAuditClient stub
  throws NotSupportedException from the new method so a regression that
  accidentally routes a cached packet through the sync stub fails loudly.
* New NoOpSiteStreamAuditClientTests cover the null-guard + empty-ack
  contract for both batch shapes.

Bundle E task E1.

src/ScadaLink.AuditLog/Site/Telemetry/ISiteStreamAuditClient.cs

@@ -20,4 +20,23 @@ public interface ISiteStreamAuditClient
     /// in the site SQLite queue.
     /// </summary>
     Task<IngestAck> IngestAuditEventsAsync(AuditEventBatch batch, CancellationToken ct);
+
+    /// <summary>
+    /// Pushes the combined <see cref="CachedTelemetryBatch"/> (Audit Log #23 / M3)
+    /// to the central <c>IngestCachedTelemetry</c> RPC. Each packet carries both
+    /// the audit row and the operational <c>SiteCalls</c> upsert; central writes
+    /// both in a single MS SQL transaction. Returns the same
+    /// <see cref="IngestAck"/> shape as <see cref="IngestAuditEventsAsync"/> so
+    /// the M3 site-side forwarder can flip the underlying audit rows to
+    /// <see cref="ScadaLink.Commons.Types.Enums.AuditForwardState.Forwarded"/>
+    /// once central has acknowledged them.
+    /// </summary>
+    /// <remarks>
+    /// The production gRPC-backed implementation lands in M6 (no site→central
+    /// gRPC channel exists today); until then the default
+    /// <see cref="NoOpSiteStreamAuditClient"/> binding returns an empty ack and
+    /// integration tests substitute a direct-actor client that routes the batch
+    /// straight into the in-process <c>AuditLogIngestActor</c>.
+    /// </remarks>
+    Task<IngestAck> IngestCachedTelemetryAsync(CachedTelemetryBatch batch, CancellationToken ct);
 }