feat(otopcua): bridge Akka actor logs into Serilog

DriverHostActor/DriverInstanceActor and cluster events log via Akka's ILoggingAdapter, which had no Serilog bridge — under the Windows service host the default StandardOutLogger output is discarded, making the driver-role actor graph invisible (this masked the data-plane diagnosis).

- Add Akka.Logger.Serilog 1.5.60 (deps satisfied by Akka 1.5.62 / Serilog 4.3.1).
- WithOtOpcUaClusterBootstrap: ConfigureLoggers(DebugLevel; ClearLoggers(); AddLogger<SerilogLogger>()) — Akka.Hosting owns logger setup, so HOCON akka.loggers alone is not honored.
- Program.cs: set static Serilog.Log.Logger from the DI root logger after Build() (AddZbSerilog registers the MEL provider but not the static logger, which the Akka SerilogLogger and the startup banner both need).

Directory.Packages.props

@@ -8,6 +8,7 @@
     <PackageVersion Include="Akka.Cluster.Hosting" Version="1.5.62" />
     <PackageVersion Include="Akka.Cluster.Tools" Version="1.5.62" />
     <PackageVersion Include="Akka.Hosting" Version="1.5.62" />
+    <PackageVersion Include="Akka.Logger.Serilog" Version="1.5.60" />
     <PackageVersion Include="Akka.Remote" Version="1.5.62" />
     <PackageVersion Include="Akka.Remote.Hosting" Version="1.5.62" />
     <PackageVersion Include="Akka.Streams" Version="1.5.62" />

src/Core/ZB.MOM.WW.OtOpcUa.Cluster/Resources/akka.conf

@@ -7,6 +7,12 @@
 # Any divergence from these defaults must be deliberate and recorded in docs/v2/Architecture.md.
 
 akka {
+    # Akka logger wiring (route ILoggingAdapter → Serilog) is configured via Akka.Hosting's
+    # ConfigureLoggers in ServiceCollectionExtensions.WithOtOpcUaClusterBootstrap — HOCON
+    # `akka.loggers` alone is not honored by Akka.Hosting. logger-startup-timeout is kept here
+    # since the Serilog logger can be slow to initialize at startup.
+    logger-startup-timeout = 30s
+
     extensions = [
         "Akka.Cluster.Tools.PublishSubscribe.DistributedPubSubExtensionProvider, Akka.Cluster.Tools"
     ]

src/Core/ZB.MOM.WW.OtOpcUa.Cluster/ServiceCollectionExtensions.cs

@@ -1,5 +1,7 @@
 using Akka.Cluster.Hosting;
+using Akka.Event;
 using Akka.Hosting;
+using Akka.Logger.Serilog;
 using Akka.Remote.Hosting;
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
@@ -53,6 +55,19 @@ public static class ServiceCollectionExtensions
 
         builder.AddHocon(HoconLoader.LoadBaseConfig(), HoconAddMode.Append);
 
+        // Route Akka's internal ILoggingAdapter (DriverHostActor, DriverInstanceActor, cluster
+        // events, …) into Serilog so those logs reach the same sinks as the MEL/Serilog application
+        // logs. Akka.Hosting owns logger setup, so HOCON `akka.loggers` alone is not honored — the
+        // logger must be registered through ConfigureLoggers. Without this the actor graph logs only
+        // to the default StandardOutLogger (discarded under the Windows service host), which is why
+        // the driver-role actors were invisible during the 2026-06 data-plane investigation.
+        builder.ConfigureLoggers(setup =>
+        {
+            setup.LogLevel = LogLevel.DebugLevel;
+            setup.ClearLoggers();
+            setup.AddLogger<SerilogLogger>();
+        });
+
         builder.WithRemoting(new RemoteOptions
         {
             HostName = options.Hostname,

src/Core/ZB.MOM.WW.OtOpcUa.Cluster/ZB.MOM.WW.OtOpcUa.Cluster.csproj

@@ -10,6 +10,7 @@
         <PackageReference Include="Akka.Cluster"/>
         <PackageReference Include="Akka.Cluster.Hosting"/>
         <PackageReference Include="Akka.Cluster.Tools"/>
+        <PackageReference Include="Akka.Logger.Serilog"/>
         <PackageReference Include="Akka.Remote.Hosting"/>
         <PackageReference Include="Microsoft.Extensions.Hosting"/>
         <PackageReference Include="Microsoft.Extensions.Options.ConfigurationExtensions"/>

src/Server/ZB.MOM.WW.OtOpcUa.Host/Program.cs

@@ -228,6 +228,14 @@ builder.Services.AddOtOpcUaHealth();
 builder.Services.AddOtOpcUaObservability(builder.Configuration);
 
 var app = builder.Build();
+
+// AddZbSerilog registers Serilog as the MEL logging provider but does NOT assign the static
+// Serilog.Log.Logger. Set it from the DI root logger so (1) static Log.* calls like the startup
+// banner below emit, and (2) Akka.Logger.Serilog's SerilogLogger — which writes to Log.Logger —
+// routes the actor graph's logs (DriverHostActor et al.) to the configured sinks. Must run before
+// app.RunAsync() starts the ActorSystem (the Akka logger captures Log.Logger at system start).
+Serilog.Log.Logger = app.Services.GetRequiredService<Serilog.ILogger>();
+
 app.UseSerilogRequestLogging();
 
 // Razor class library static assets (_content/<libname>/...) are served via endpoint