feat(reconcile): site-reconcile messages + expected-set/stage-if-absent repo

- Commons: ReconcileSiteRequest / ReconcileSiteResponse / ReconcileGapItem
  message contracts (site→central ClusterClient on startup; central reply with
  gap fetch tokens + orphan list + base URL).
- Commons: ExpectedDeployment projection record (Commons/Types/Deployment/),
  lightweight join of DeployedConfigSnapshot + Instance (no ConfigJson).
- IDeploymentManagerRepository: GetExpectedDeploymentsForSiteAsync (inner-join
  query returning deployed set for a site, excluding snapshot-less instances) +
  StagePendingIfAbsentAsync (insert-if-absent, self-contained save, returns bool;
  does NOT supersede — an existing pending row signals in-flight delivery).
- DeploymentManagerRepository: implement both methods; StagePendingIfAbsent
  commits internally (matches PurgeExpiredPendingDeployments convention).
- ReconcileRepositoryTests: 4 tests covering expected-set filter/IsEnabled/
  cross-site isolation, empty-site, stage-absent (true + row retrievable),
  stage-present (false + existing row unchanged); all pass.

src/ZB.MOM.WW.ScadaBridge.Commons/Types/Deployment/ExpectedDeployment.cs

@@ -0,0 +1,19 @@
+namespace ZB.MOM.WW.ScadaBridge.Commons.Types.Deployment;
+
+/// <summary>
+/// Lightweight projection of an instance's last-deployed state, used by the startup-reconciliation
+/// path to compute the gap between central's expected deployed set and a site node's local inventory.
+/// No <c>ConfigurationJson</c> is included — the full config is only fetched for gap instances via
+/// the HTTP endpoint using the freshly-minted <see cref="ReconcileGapItem.FetchToken"/>.
+/// </summary>
+/// <param name="InstanceId">The instance primary key.</param>
+/// <param name="InstanceUniqueName">The system-wide unique name for the instance.</param>
+/// <param name="RevisionHash">Revision hash of the flattened configuration at last successful deploy.</param>
+/// <param name="DeploymentId">Deployment ID of the last successful deploy (the fetch key).</param>
+/// <param name="IsEnabled">True when the instance's current <c>State</c> is <c>Enabled</c>.</param>
+public record ExpectedDeployment(
+    int InstanceId,
+    string InstanceUniqueName,
+    string RevisionHash,
+    string DeploymentId,
+    bool IsEnabled);