feat(room-combiner): add room-combination operation status lifecycle

Port the in-progress room-combination lockout feature from the v2 line (v2.43.0-feature-in-progress-lockout-updates.1) onto the v3 async combiner. The server-side lifecycle was absent from v3; the React overlay and codec Navigator webview were already present on v3 but never triggered because Essentials never emitted the status.

- Add IEssentialsRoomCombinerWithOperationStatus + CombinationOperationStatus (OperationId/ScenarioKey/StartedUtc/State/Message/AffectedRoomKeys) and the CombinationOperationState enum.

- EssentialsRoomCombiner publishes InProgress on ChangeScenario, gates completion on reflective ScenarioReconciled providers, supports a configurable operation timeout, and computes AffectedRoomKeys by diffing scenario uiMaps.

- Broadcast combinationOperation over the room-combiner messenger (status-changed event + full status).

- Guard PartitionPresent getter against a null partition sensor.

Preserves the exact member/JSON names the codec (reflection) and React (JSON) clients bind to: CombinationOperation, State, AffectedRoomKeys, CombinationOperationStatusChanged, combinationOperation.{state,affectedRoomKeys}.

Author: erikdred

src/PepperDash.Essentials.Core/PartitionSensor/EssentialsPartitionController.cs

@@ -24,7 +24,7 @@ public bool PartitionPresent
         {
             if (IsInAutoMode)
             {
-                return _partitionSensor.PartitionPresentFeedback.BoolValue;
+                return _partitionSensor?.PartitionPresentFeedback?.BoolValue ?? _partitionPresent;
             }
 
             return _partitionPresent;