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.Host/Actors/DeadLetterMonitorActor.cs

@@ -0,0 +1,65 @@
+using Akka.Actor;
+using Akka.Event;
+using Microsoft.Extensions.Logging;
+using ZB.MOM.WW.ScadaBridge.HealthMonitoring;
+
+namespace ZB.MOM.WW.ScadaBridge.Host.Actors;
+
+/// <summary>
+/// Subscribes to Akka.NET dead letter events, logs them, and tracks count
+/// for health monitoring integration.
+/// </summary>
+public class DeadLetterMonitorActor : ReceiveActor
+{
+    private long _deadLetterCount;
+    private readonly ISiteHealthCollector? _healthCollector;
+
+    /// <summary>
+    /// Initializes the actor and registers dead-letter message handlers.
+    /// </summary>
+    /// <param name="logger">Logger for dead-letter events.</param>
+    /// <param name="healthCollector">Optional health collector used to increment the dead-letter metric.</param>
+    public DeadLetterMonitorActor(ILogger<DeadLetterMonitorActor> logger, ISiteHealthCollector? healthCollector = null)
+    {
+        _healthCollector = healthCollector;
+
+        Receive<DeadLetter>(dl =>
+        {
+            _deadLetterCount++;
+            _healthCollector?.IncrementDeadLetter();
+            logger.LogWarning(
+                "Dead letter: {MessageType} from {Sender} to {Recipient}",
+                dl.Message.GetType().Name,
+                dl.Sender,
+                dl.Recipient);
+        });
+
+        Receive<GetDeadLetterCount>(_ => Sender.Tell(new DeadLetterCountResponse(_deadLetterCount)));
+    }
+
+    /// <inheritdoc />
+    protected override void PreStart()
+    {
+        Context.System.EventStream.Subscribe(Self, typeof(DeadLetter));
+    }
+
+    /// <inheritdoc />
+    protected override void PostStop()
+    {
+        Context.System.EventStream.Unsubscribe(Self, typeof(DeadLetter));
+    }
+}
+
+/// <summary>
+/// Message to request the current dead letter count.
+/// </summary>
+public sealed class GetDeadLetterCount
+{
+    public static readonly GetDeadLetterCount Instance = new();
+    private GetDeadLetterCount() { }
+}
+
+/// <summary>
+/// Response containing the current dead letter count.
+/// </summary>
+public sealed record DeadLetterCountResponse(long Count);