feat(scripts): realign Test Run with runtime API, add anonymous-object calls and instance binding

The Test Run sandbox and Monaco analysis modelled a script API that had
drifted from the site runtime's ScriptGlobals, so real scripts failed to
compile in Test Run. Realign both to the runtime surface
(Instance/Scripts/ExternalSystem/Attributes/Children/Parent) and drop the
duplicate ScriptHost stub so the two cannot diverge again.

- Script calls (Scripts.CallShared, Instance.CallScript, Route.To().Call)
  accept an anonymous object instead of a hand-built dictionary, via a
  shared ScriptArgs normalizer; existing dictionary calls still compile.
- Test Run can optionally bind to a deployed instance, so Instance/
  Attributes/CallScript route to it cross-site; adds site-side
  RouteToGetAttributes/RouteToSetAttributes handlers.
- Adds Test Run panels to the API method and template script editors.
- Fixes the TestDatabaseQuery seed script, which queried a table that
  never existed.

Also commits unrelated in-progress work already in the tree: the health
monitoring report loop, site streaming changes, and the Admin/Design
data-connection and SMTP page reorganization.

src/ScadaLink.HealthMonitoring/SiteHealthState.cs

@@ -9,7 +9,21 @@ public class SiteHealthState
 {
     public required string SiteId { get; init; }
     public SiteHealthReport LatestReport { get; set; } = null!;
+
+    /// <summary>
+    /// Time the latest full <see cref="SiteHealthReport"/> was processed.
+    /// Used by the UI to surface report staleness during failover.
+    /// </summary>
     public DateTimeOffset LastReportReceivedAt { get; set; }
+
+    /// <summary>
+    /// Time the most recent signal of any kind (full report OR ~5s heartbeat)
+    /// was received. Drives offline detection — heartbeats from the standby
+    /// keep the site marked online even when the active node is unable to
+    /// produce a report (mid-failover, brief stalls).
+    /// </summary>
+    public DateTimeOffset LastHeartbeatAt { get; set; }
+
     public long LastSequenceNumber { get; set; }
     public bool IsOnline { get; set; }
 }