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/Dashboard/Hubs/EventsHub.cs

@@ -21,6 +21,9 @@ public sealed class EventsHub : Hub
     /// <summary>Method name used to push individual <c>MxEvent</c> values to clients.</summary>
     public const string EventMessage = "MxEvent";
 
+    /// <summary>Computes the SignalR group name for a given session id.</summary>
+    /// <param name="sessionId">The session id.</param>
+    /// <returns>The group name for the session.</returns>
     public static string GroupName(string sessionId) => $"session:{sessionId}";
 
     /// <summary>
@@ -56,6 +59,9 @@ public sealed class EventsHub : Hub
         return Groups.AddToGroupAsync(Context.ConnectionId, GroupName(sessionId));
     }
 
+    /// <summary>Unsubscribes the calling SignalR connection from the per-session events group.</summary>
+    /// <param name="sessionId">Session id to unsubscribe the caller from.</param>
+    /// <returns>A task representing the unsubscription operation.</returns>
     public Task UnsubscribeSession(string sessionId)
     {
         if (string.IsNullOrWhiteSpace(sessionId))