docs+ui: backfill XML doc comments and finish dashboard layout pass

Adds missing <summary>/<param> XML docs across 99 server, worker, and test
files so CommentChecker reports zero issues (TreatWarningsAsErrors needs the
analyzer clean). Bundles in WIP dashboard work: NavSection extraction,
MainLayout/site.css/js styling alignment, and DashboardOptions/Auth tweaks.

src/ZB.MOM.WW.MxGateway.Server/Sessions/SessionLeaseMonitorHostedService.cs

@@ -13,6 +13,7 @@ public sealed class SessionLeaseMonitorHostedService(
 {
     private readonly TimeProvider _timeProvider = timeProvider ?? TimeProvider.System;
 
+    /// <inheritdoc />
     protected override async Task ExecuteAsync(CancellationToken stoppingToken)
     {
         TimeSpan interval = TimeSpan.FromSeconds(Math.Max(1, options.Value.Sessions.LeaseSweepIntervalSeconds));