feat(sitecallaudit): query, KPI and detail backend for the Site Calls page

src/ScadaLink.Commons/Interfaces/Repositories/ISiteCallAuditRepository.cs

@@ -63,4 +63,27 @@ public interface ISiteCallAuditRepository
     /// deleted.
     /// </summary>
     Task<int> PurgeTerminalAsync(DateTime olderThanUtc, CancellationToken ct = default);
+
+    /// <summary>
+    /// Computes a point-in-time global <see cref="SiteCallKpiSnapshot"/> from the
+    /// <c>SiteCalls</c> table. Counts are aggregated server-side (no row
+    /// materialisation): <c>StuckCount</c> uses <paramref name="stuckCutoff"/>;
+    /// <c>FailedLastInterval</c> / <c>DeliveredLastInterval</c> use
+    /// <paramref name="intervalSince"/>; the current time for <c>OldestPendingAge</c>
+    /// is captured inside the method.
+    /// </summary>
+    Task<SiteCallKpiSnapshot> ComputeKpisAsync(
+        DateTime stuckCutoff,
+        DateTime intervalSince,
+        CancellationToken ct = default);
+
+    /// <summary>
+    /// Computes a point-in-time <see cref="SiteCallSiteKpiSnapshot"/> per source
+    /// site. Sites with no <c>SiteCalls</c> rows at all are omitted. The stuck
+    /// cutoff and interval bounds are interpreted as in <see cref="ComputeKpisAsync"/>.
+    /// </summary>
+    Task<IReadOnlyList<SiteCallSiteKpiSnapshot>> ComputePerSiteKpisAsync(
+        DateTime stuckCutoff,
+        DateTime intervalSince,
+        CancellationToken ct = default);
 }