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/DashboardSessionAdminResult.cs

@@ -4,11 +4,15 @@ public sealed record DashboardSessionAdminResult(
     bool Succeeded,
     string Message)
 {
+    /// <summary>Creates a successful result with the given message.</summary>
+    /// <param name="message">The result message.</param>
     public static DashboardSessionAdminResult Success(string message)
     {
         return new DashboardSessionAdminResult(true, message);
     }
 
+    /// <summary>Creates a failed result with the given message.</summary>
+    /// <param name="message">The result message.</param>
     public static DashboardSessionAdminResult Fail(string message)
     {
         return new DashboardSessionAdminResult(false, message);