refactor(logging): adopt ZB.MOM.WW.Telemetry.Serilog bootstrap

Swap the gateway process logging from the default Microsoft.Extensions.Logging
provider onto the shared ZB.MOM.WW.Telemetry.Serilog two-stage bootstrap.

- Add a cross-repo ProjectReference to ZB.MOM.WW.Telemetry.Serilog (transitively
  brings the Telemetry core package); the referenced project resolves its own
  Directory.Build.props / Directory.Packages.props so it does not perturb this build.
- Replace MEL wiring in GatewayApplication with builder.AddZbSerilog(ServiceName=
  "mxgateway"; SiteId/NodeRole read from MxGateway:Telemetry when present) and add
  app.UseSerilogRequestLogging().
- Add a Serilog section (Console + daily rolling File sinks, MinimumLevel) to
  appsettings.json and a MinimumLevel override to appsettings.Development.json,
  replacing the old MEL Logging sections.

The net48/x86 worker is untouched. Correlation scope + redaction move to the
shared ILogRedactor seam in the follow-up commit.

src/ZB.MOM.WW.MxGateway.Server/GatewayApplication.cs

@@ -1,4 +1,5 @@
 using Microsoft.AspNetCore.Hosting.StaticWebAssets;
+using Serilog;
 using ZB.MOM.WW.MxGateway.Contracts;
 using ZB.MOM.WW.MxGateway.Server.Alarms;
 using ZB.MOM.WW.MxGateway.Server.Configuration;
@@ -11,6 +12,7 @@ using ZB.MOM.WW.MxGateway.Server.Security.Authentication;
 using ZB.MOM.WW.MxGateway.Server.Security.Authorization;
 using ZB.MOM.WW.MxGateway.Server.Sessions;
 using ZB.MOM.WW.MxGateway.Server.Workers;
+using ZB.MOM.WW.Telemetry.Serilog;
 
 namespace ZB.MOM.WW.MxGateway.Server;
 
@@ -31,7 +33,10 @@ public static class GatewayApplication
         WebApplicationBuilder builder = CreateBuilder(args);
         WebApplication app = builder.Build();
 
+        // Push the per-request correlation properties (via Serilog LogContext) before the
+        // request-logging middleware emits its completion event, so those properties appear on it.
         app.UseGatewayRequestLoggingScope();
+        app.UseSerilogRequestLogging();
         app.UseStaticFiles();
         app.UseAuthentication();
         app.UseAuthorization();
@@ -55,6 +60,8 @@ public static class GatewayApplication
         });
         StaticWebAssetsLoader.UseStaticWebAssets(builder.Environment, builder.Configuration);
 
+        ConfigureSerilog(builder);
+
         builder.Services.AddGatewayConfiguration();
         builder.Services.AddSqliteAuthStore();
         builder.Services.AddGatewayGrpcAuthorization();
@@ -72,6 +79,26 @@ public static class GatewayApplication
         return builder;
     }
 
+    /// <summary>
+    /// Replaces the default Microsoft.Extensions.Logging provider with the shared
+    /// <c>ZB.MOM.WW.Telemetry.Serilog</c> bootstrap (<see cref="ZbSerilogExtensions.AddZbSerilog"/>).
+    /// Sinks and minimum level come from the <c>Serilog</c> configuration section; identity
+    /// (<c>SiteId</c>/<c>NodeRole</c>) is read from <c>MxGateway:Telemetry</c> when present.
+    /// </summary>
+    /// <param name="builder">The web application builder being configured.</param>
+    private static void ConfigureSerilog(WebApplicationBuilder builder)
+    {
+        string? siteId = builder.Configuration["MxGateway:Telemetry:SiteId"];
+        string? nodeRole = builder.Configuration["MxGateway:Telemetry:NodeRole"];
+
+        builder.AddZbSerilog(options =>
+        {
+            options.ServiceName = "mxgateway";
+            options.SiteId = string.IsNullOrWhiteSpace(siteId) ? null : siteId;
+            options.NodeRole = string.IsNullOrWhiteSpace(nodeRole) ? null : nodeRole;
+        });
+    }
+
     private static string ResolveContentRootPath()
     {
         string? configuredContentRootPath = Environment.GetEnvironmentVariable("ASPNETCORE_CONTENTROOT");