fix(transport): export instance AreaName — Area-by-name reconciliation was half-shipped (exporter hardcoded null)

Claude-Session: https://claude.ai/code/session_01MtdgwpEeCUn6cUA5f1LMPj

src/ZB.MOM.WW.ScadaBridge.Transport/Serialization/EntityDtos.cs

@@ -41,6 +41,15 @@ public sealed record EntityAggregate(
     // and never sees null; producers that resolve SMS config opt in via
     // object-initializer.
     public IReadOnlyList<SmsConfiguration> SmsConfigurations { get; init; } = Array.Empty<SmsConfiguration>();
+
+    // Area id → name lookup for the exported instances. Areas are not carried as a
+    // first-class bundle collection (they reconcile by NAME under the target site),
+    // so the aggregate only needs enough to resolve each instance's AreaId FK back to
+    // a portable name at serialization time. Init-only with an empty default: producers
+    // that export instances populate it; every other caller keeps compiling and the
+    // serializer emits AreaName: null when an instance's AreaId isn't in the map.
+    public IReadOnlyDictionary<int, string> AreaNameById { get; init; } =
+        new Dictionary<int, string>();
 }
 
 /// <summary>

src/ZB.MOM.WW.ScadaBridge.Transport/Serialization/EntitySerializer.cs

@@ -248,10 +248,13 @@ public sealed class EntitySerializer
                 UniqueName: inst.UniqueName,
                 TemplateName: templateNameById.TryGetValue(inst.TemplateId, out var tn) ? tn : string.Empty,
                 SiteIdentifier: siteIdentifierBySiteId.TryGetValue(inst.SiteId, out var isid) ? isid : string.Empty,
-                // TODO: Areas don't travel in the bundle yet — EntityAggregate
-                // carries no Areas collection, so there's no id→name lookup. Emit
-                // null until area transport is added; the importer leaves AreaId null.
-                AreaName: null,
+                // Area travels by NAME — the importer resolves-or-creates the
+                // equivalent area under the target site (ResolveOrCreateAreaIdAsync).
+                // Resolve the instance's AreaId FK against the aggregate's id→name
+                // map; if the FK is null (no area) or unresolved (orphan/absent from
+                // the map), the name comes through as null and the importer leaves
+                // AreaId null on the imported instance.
+                AreaName: inst.AreaId is { } aid && aggregate.AreaNameById.TryGetValue(aid, out var an) ? an : null,
                 State: inst.State,
                 AttributeOverrides: inst.AttributeOverrides.Select(o => new InstanceAttributeOverrideDto(
                     AttributeName: o.AttributeName,