feat(kpihistory): route long-range KPI queries to hourly rollups by threshold (plan #22 T5)

GetSeriesAsync now branches on window width: windows wider than
RollupThresholdHours (default 168h/7d) read pre-aggregated hourly rollups
via GetHourlySeriesAsync; windows at or below the threshold read raw
samples via GetRawSeriesAsync (preserving intra-minute detail on 24h/7d).
The boundary is strict greater-than, so exactly 168h stays on the raw
path. KpiSeriesBucketer.Bucket runs unchanged on whichever series (a 90d
rollup can still exceed the point ceiling). Both ctors route identically
via a shared FetchSeriesAsync helper reading _options.RollupThresholdHours,
the same options instance that already supplies DefaultMaxSeriesPoints.
GetSeriesAsync public signature unchanged.

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

src/ZB.MOM.WW.ScadaBridge.CentralUI/Services/KpiHistoryQueryService.cs

@@ -79,17 +79,39 @@ public sealed class KpiHistoryQueryService : IKpiHistoryQueryService
         // Test-seam ctor: use the injected repository directly.
         if (_injectedRepository is not null)
         {
-            var injectedRaw = await _injectedRepository.GetRawSeriesAsync(
-                source, metric, scope, scopeKey, fromUtc, toUtc, cancellationToken);
-            return KpiSeriesBucketer.Bucket(injectedRaw, fromUtc, toUtc, effectiveMax);
+            var injectedSeries = await FetchSeriesAsync(
+                _injectedRepository, source, metric, scope, scopeKey, fromUtc, toUtc, cancellationToken);
+            return KpiSeriesBucketer.Bucket(injectedSeries, fromUtc, toUtc, effectiveMax);
         }
 
         // Production: a fresh scope (and thus a fresh DbContext) per query so a
         // chart's auto-load never shares the circuit-scoped context.
         await using var serviceScope = _scopeFactory!.CreateAsyncScope();
         var repository = serviceScope.ServiceProvider.GetRequiredService<IKpiHistoryRepository>();
-        var raw = await repository.GetRawSeriesAsync(
-            source, metric, scope, scopeKey, fromUtc, toUtc, cancellationToken);
-        return KpiSeriesBucketer.Bucket(raw, fromUtc, toUtc, effectiveMax);
+        var series = await FetchSeriesAsync(
+            repository, source, metric, scope, scopeKey, fromUtc, toUtc, cancellationToken);
+        return KpiSeriesBucketer.Bucket(series, fromUtc, toUtc, effectiveMax);
+    }
+
+    /// <summary>
+    /// Routes a series fetch to the raw-sample or hourly-rollup repository method by
+    /// the requested window width. Windows wider than
+    /// <see cref="KpiHistoryOptions.RollupThresholdHours"/> read the pre-aggregated
+    /// hourly rollups (≈60× fewer rows scanned on 30 d/90 d ranges); windows at or below
+    /// the threshold read raw samples, preserving intra-minute detail on the 24 h/7 d
+    /// charts. Both paths return the same ascending <see cref="KpiSeriesPoint"/> shape, so
+    /// the caller's <see cref="KpiSeriesBucketer.Bucket"/> step is agnostic to the source
+    /// (a 90 d rollup can still exceed the point ceiling, so bucketing still applies).
+    /// The boundary is strict: exactly <c>RollupThresholdHours</c> stays on the raw path.
+    /// </summary>
+    private Task<IReadOnlyList<KpiSeriesPoint>> FetchSeriesAsync(
+        IKpiHistoryRepository repository,
+        string source, string metric, string scope, string? scopeKey,
+        DateTime fromUtc, DateTime toUtc, CancellationToken cancellationToken)
+    {
+        var windowHours = (toUtc - fromUtc).TotalHours;
+        return windowHours > _options.RollupThresholdHours
+            ? repository.GetHourlySeriesAsync(source, metric, scope, scopeKey, fromUtc, toUtc, cancellationToken)
+            : repository.GetRawSeriesAsync(source, metric, scope, scopeKey, fromUtc, toUtc, cancellationToken);
     }
 }