feat: add CLI debug snapshot command for one-shot instance state inspection

Adds `debug snapshot --id <int>` to query a running instance's current
attribute values and alarm states without the subscribe/stream overhead
of the debug view. Routes through ManagementActor → CommunicationService
→ site DeploymentManager → InstanceActor using the existing remote query
pattern.

src/ScadaLink.Communication/Actors/SiteCommunicationActor.cs

@@ -104,6 +104,9 @@ public class SiteCommunicationActor : ReceiveActor, IWithTimers
         Receive<SubscribeDebugViewRequest>(msg => _deploymentManagerProxy.Forward(msg));
         Receive<UnsubscribeDebugViewRequest>(msg => _deploymentManagerProxy.Forward(msg));
 
+        // Pattern 6a: Debug Snapshot (one-shot) — forward to Deployment Manager
+        Receive<DebugSnapshotRequest>(msg => _deploymentManagerProxy.Forward(msg));
+
         // Pattern 7: Remote Queries
         Receive<EventLogQueryRequest>(msg =>
         {