fix(kpihistory)+fix(notificationoutbox)+fix(sitecallaudit)+fix(host): P5-5 — rate-fold interval triple made self-consistent + cross-validated

Defect: the hourly KPI rollup fold (KpiHistoryRepository.FoldHourlyRollupsAsync)
sums every Rate-classified sample recorded in an hour, correct only if each
sample is a non-overlapping delta covering exactly one recorder tick
(KpiHistoryOptions.SampleInterval). That invariant was an unenforced silent
assumption across three independently-owned config keys — SampleInterval,
NotificationOutboxOptions.DeliveredKpiWindow, SiteCallAuditOptions.KpiInterval —
so widening DeliveredKpiWindow to e.g. 15 min would silently over-count the
rollup ~15x.

Robust fix: NotificationOutboxKpiSampleSource and SiteCallAuditKpiSampleSource
now rescale their Rate-classified samples (deliveredLastInterval,
failedLastInterval) by SampleInterval / (DeliveredKpiWindow or KpiInterval)
before recording, so the rollup's per-hour Sum is correct regardless of how
the other two keys are tuned — the live dashboard tile's own cutoff/window is
untouched. Both sources gain a project reference to KpiHistory to read
SampleInterval; no cycle (KpiHistory references only Commons).

Eager cross-validation (defense-in-depth): KpiRateFoldIntervalCrossValidator
(Host, the one composition root referencing all three component projects)
fails boot naming all three config keys when they diverge, protecting the
separate (still-real) invariant that the recorded/charted KPI-history sample
equals the live tile at the same instant — which the rescale trades away
whenever the scale factor isn't 1. Rides KpiHistoryOptions' existing
ValidateOnStart trigger.

Also: NotificationOutboxOptions had no registered validator at all before this
(the gap this task's "whichever options class owns DeliveredKpiWindow" file
scope pointed at) — added NotificationOutboxOptionsValidator mirroring
SiteCallAuditOptionsValidator's positive-duration/count convention, wired with
ValidateOnStart.

Tests: new rescale tests in both sample-source suites prove the fold is
numerically correct at a non-default SampleInterval (30/40 counted over a
15/20-minute window correctly divides down to a 1-minute-tick delta); new
KpiRateFoldIntervalCrossValidatorTests prove divergent config fails with all
three keys named; new NotificationOutboxOptionsValidatorTests. Every new test
proven to fail against the unfixed computation first (temporarily
short-circuited the scale factor / cross-check to the pre-fix behavior,
confirmed failure, restored) — not via git stash (repo-wide, shared across
concurrent worktrees this session) but via file-copy swap.

Full suites green: Host.Tests (527), ConfigurationDatabase.Tests (401),
KpiHistory.Tests (54), NotificationOutbox.Tests (163),
SiteCallAudit.Tests (67).

src/ZB.MOM.WW.ScadaBridge.NotificationOutbox/ServiceCollectionExtensions.cs

@@ -56,8 +56,16 @@ public static class ServiceCollectionExtensions
     {
         ArgumentNullException.ThrowIfNull(services);
 
+        // Eager startup validation (arch-review §1.5 / P5-5): this options class had no
+        // registered validator before — ValidateOnStart makes a bad
+        // ScadaBridge:NotificationOutbox section fail fast at boot with a clear,
+        // key-naming message instead of spinning a scheduler or, for DeliveredKpiWindow,
+        // dividing by zero in NotificationOutboxKpiSampleSource's KpiHistory rescale.
         services.AddOptions<NotificationOutboxOptions>()
-            .BindConfiguration(OptionsSection);
+            .BindConfiguration(OptionsSection)
+            .ValidateOnStart();
+        services.TryAddEnumerable(
+            ServiceDescriptor.Singleton<IValidateOptions<NotificationOutboxOptions>, NotificationOutboxOptionsValidator>());
 
         // Bind + validate SmsOptions (ScadaBridge:Sms): the SMS adapter's body cap and
         // per-request timeout fallback. ValidateOnStart surfaces a bad option at host