feat(historian): advertise only the backend's aggregates under AggregateFunctions (#682)

IHistorianDataSource.SupportedAggregates (default: every HistoryAggregateType)
is the one authority for both ServerCapabilities/AggregateFunctions (i=2997) and
HistoryServerCapabilities/AggregateFunctions (i=11201) and for the up-front
BadAggregateNotSupported in HistoryRead-Processed. Gateway declares
AggregateModeMapper.Served (4), SqlServer/QuestDB AggregateFamilies.Served (17),
Null none. Only the folder references are trimmed; the SDK's calculator
factories stay so live AggregateFilter subscriptions keep working.

Co-Authored-By: Claude <noreply@anthropic.com>

src/Server/ZB.MOM.WW.OtOpcUa.OpcUaServer/OtOpcUaSdkServer.cs

@@ -200,6 +200,21 @@ public sealed class OtOpcUaSdkServer : StandardServer
         return true;
     }
 
+    /// <summary>
+    ///     Gitea #682 — keep the SDK's full set of calculator factories (live-data <c>AggregateFilter</c> subscriptions
+    ///     need them), then trim the advertised <c>AggregateFunctions</c> folders to the node manager's current historian
+    ///     source. At this point that is the Null default (no aggregates); the Host's
+    ///     <see cref="SetHistorianDataSource"/> re-syncs to the configured backend's set right after start.
+    /// </summary>
+    /// <inheritdoc />
+    protected override AggregateManager CreateAggregateManager(
+        IServerInternal server, ApplicationConfiguration configuration)
+    {
+        var manager = base.CreateAggregateManager(server, configuration);
+        _otOpcUaNodeManager?.SyncAdvertisedAggregates();
+        return manager;
+    }
+
     /// <inheritdoc />
     protected override MasterNodeManager CreateMasterNodeManager(
         IServerInternal server, ApplicationConfiguration configuration)