refactor: rename ScadaLink → ZB.MOM.WW.ScadaBridge (code + projects + namespaces)

Solution + 23 src projects + 26 test projects renamed; folders, csproj,
namespaces, and ScadaLinkDbContext/ScadaBridgeDbContext class updated.
ActorSystem "scadalink" → "scadabridge", Akka seed-node URLs migrated.
SQL roles/logins, LDAP domains, CLI command name, and CLI config dir
(~/.scadalink → ~/.scadabridge) also renamed.

Build green; 5 Host.Tests fail awaiting SQL login rename in next commit.
Pre-existing StaleTagMonitor timing flakes unchanged.

Rename script committed at tools/rename-to-scadabridge.sh.

src/ZB.MOM.WW.ScadaBridge.HealthMonitoring/SiteHealthState.cs

@@ -0,0 +1,47 @@
+using ZB.MOM.WW.ScadaBridge.Commons.Messages.Health;
+
+namespace ZB.MOM.WW.ScadaBridge.HealthMonitoring;
+
+/// <summary>
+/// In-memory state for a single site's health, stored by the central aggregator.
+/// Immutable: every state transition produces a new instance which the aggregator
+/// installs into its <c>ConcurrentDictionary</c> via an atomic compare-and-swap.
+/// This makes handing the reference straight to UI callers safe — a consumer can
+/// never observe a torn or half-applied update.
+/// </summary>
+public sealed record SiteHealthState
+{
+    /// <summary>Gets the unique identifier of the site this state record belongs to.</summary>
+    public required string SiteId { get; init; }
+
+    /// <summary>
+    /// The latest full <see cref="SiteHealthReport"/> received for the site, or
+    /// <c>null</c> if the site is known only via heartbeats and has not yet sent
+    /// a report.
+    /// </summary>
+    public SiteHealthReport? LatestReport { get; init; }
+
+    /// <summary>
+    /// Time the latest full <see cref="SiteHealthReport"/> was processed, or
+    /// <c>null</c> if the site is known only via heartbeats and has not yet sent
+    /// a report. Used by the UI to surface report staleness during failover;
+    /// the <c>null</c> case must be rendered as "no report yet" rather than as a
+    /// timestamp (a <c>default</c> sentinel would display as year-0001).
+    /// </summary>
+    public DateTimeOffset? LastReportReceivedAt { get; init; }
+
+    /// <summary>
+    /// Time the most recent signal of any kind (full report OR 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). Heartbeat cadence is owned by the Cluster
+    /// Infrastructure / SiteCommunicationActor (every
+    /// CommunicationOptions.TransportHeartbeatInterval — 5s by default).
+    /// </summary>
+    public DateTimeOffset LastHeartbeatAt { get; init; }
+
+    /// <summary>Gets the sequence number of the last accepted health report, used to reject out-of-order duplicates.</summary>
+    public long LastSequenceNumber { get; init; }
+    /// <summary>Gets a value indicating whether the site is currently considered online.</summary>
+    public bool IsOnline { get; init; }
+}