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/wwwroot/js/nav-state.js

@@ -0,0 +1,19 @@
+// Sidebar nav collapse state — persisted in the `mxgateway_nav` cookie so it
+// survives full page reloads and reconnects. Invoked from MainLayout.razor via
+// JS interop (window.navState.get / .set). Pattern lifted from ScadaLink
+// CentralUI's wwwroot/js/nav-state.js.
+window.navState = {
+    // Returns the raw cookie value (comma-separated expanded section ids), or
+    // an empty string when the cookie is absent.
+    get: function () {
+        const match = document.cookie.match(/(?:^|;\s*)mxgateway_nav=([^;]*)/);
+        return match ? decodeURIComponent(match[1]) : "";
+    },
+    // Writes the cookie with a one-year lifetime. SameSite=Lax; not HttpOnly
+    // (JS must write it) and not sensitive.
+    set: function (value) {
+        const oneYearSeconds = 60 * 60 * 24 * 365;
+        document.cookie = "mxgateway_nav=" + encodeURIComponent(value) +
+            ";path=/;max-age=" + oneYearSeconds + ";samesite=lax";
+    }
+};