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/Components/Layout/NavSection.razor

@@ -0,0 +1,35 @@
+@* A collapsible sidebar nav section. The header is a full-width button that
+   toggles ChildContent visibility. Pattern lifted from ScadaLink CentralUI
+   (Components/Layout/NavSection.razor) — see [[project-deployed-service]]. *@
+
+<li class="nav-item">
+    <button type="button"
+            class="nav-section-toggle"
+            @onclick="OnToggle"
+            aria-expanded="@(Expanded ? "true" : "false")">
+        <span class="chevron" aria-hidden="true">@(Expanded ? "▾" : "▸")</span>
+        <span>@Title</span>
+    </button>
+</li>
+@if (Expanded)
+{
+    @ChildContent
+}
+
+@code {
+    /// <summary>Section label shown in the header (e.g. "Runtime").</summary>
+    [Parameter, EditorRequired]
+    public string Title { get; set; } = string.Empty;
+
+    /// <summary>Whether the section is expanded — its items rendered.</summary>
+    [Parameter]
+    public bool Expanded { get; set; }
+
+    /// <summary>Raised when the header button is clicked.</summary>
+    [Parameter]
+    public EventCallback OnToggle { get; set; }
+
+    /// <summary>The section's nav items, rendered only while expanded.</summary>
+    [Parameter]
+    public RenderFragment? ChildContent { get; set; }
+}