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/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.SqlServer/SqlServerHistorianDataSource.cs

@@ -316,6 +316,10 @@ public sealed class SqlServerHistorianDataSource : IHistorianDataSource
     /// <remarks>Reverse events reads are served natively (<c>ORDER BY … DESC</c>, Gitea #675).</remarks>
     public bool SupportsReverseEvents => true;
 
+    /// <inheritdoc />
+    /// <remarks>The seventeen <see cref="AggregateFamilies.Served"/> — shared with the other SQL backend (#682).</remarks>
+    public IReadOnlySet<HistoryAggregateType> SupportedAggregates => AggregateFamilies.Served;
+
 
     /// <inheritdoc />
     /// <remarks>