feat(mesh-phase4): DriverHostActor runs ConfigDb-free (LocalDb alarm store, guarded acks)

Nullable ConfigDb factory; UpsertNodeDeploymentState no-ops when absent
(central persists acks from the ApplyAck); scripted-alarm condition state
served from the LocalDb store instead of the ConfigDb-backed Ef store.
Combines Phase-4 Tasks 4 + 6. Removes the interim dbFactory! cast.

Claude-Session: https://claude.ai/code/session_01GASWkNEi68FSCtvr6rLoEW

tests/Server/ZB.MOM.WW.OtOpcUa.Host.IntegrationTests/LocalDbWiringTests.cs

@@ -11,7 +11,9 @@ using ZB.MOM.WW.LocalDb.Replication;
 using ZB.MOM.WW.OtOpcUa.Host.Configuration;
 using ZB.MOM.WW.OtOpcUa.Host.Health;
 using ZB.MOM.WW.OtOpcUa.Host.Observability;
+using ZB.MOM.WW.OtOpcUa.Core.ScriptedAlarms;
 using ZB.MOM.WW.OtOpcUa.Runtime.DeploymentCache;
+using ZB.MOM.WW.OtOpcUa.Runtime.ScriptedAlarms;
 
 namespace ZB.MOM.WW.OtOpcUa.Host.IntegrationTests;
 
@@ -107,6 +109,18 @@ public sealed class LocalDbWiringTests : IDisposable
             .ShouldBeOfType<LocalDbDeploymentArtifactCache>();
     }
 
+    [Fact]
+    public void DriverGraph_AlarmStateStoreResolvesToTheLocalDbBackedImplementation()
+    {
+        // Phase 4: scripted-alarm condition state is served from the replicated LocalDb store on a
+        // driver node. A dropped registration would silently fall the actor back to the EF store (or,
+        // DB-less, skip the alarm host) — this pins the LocalDb store as the resolved implementation.
+        var sp = BuildDriverGraph();
+
+        sp.GetService<IAlarmStateStore>()
+            .ShouldBeOfType<LocalDbAlarmConditionStateStore>();
+    }
+
     [Fact]
     public void DriverGraph_DefaultOff_SyncStatusReportsNotConnectedAndNoPeer()
     {
@@ -142,6 +156,8 @@ public sealed class LocalDbWiringTests : IDisposable
 
         sp.GetService<ILocalDb>().ShouldBeNull();
         sp.GetService<IDeploymentArtifactCache>().ShouldBeNull();
+        // Phase 4: an admin-only node never registers the LocalDb alarm store either.
+        sp.GetService<IAlarmStateStore>().ShouldBeNull();
 
         // The unconditionally-registered health check must still resolve and construct — it is meant
         // to no-op to Healthy when LocalDb is absent, not to fail because ISyncStatus is missing.