Match page width to sso-manager-node; gate Audit nav to admins

- Dashboard, Sessions, and Audit pages now wrap their content in
  <div class="container mt-4">, matching sso-manager-node/proxy's width
  instead of rendering full-bleed inside the fluid shell.
- Audit's nav entry now carries groups: ['admin'] (utils/ui.js), reusing
  the existing synthetic-admin-group nav-gating convention -- the API
  route was already server-side admin-gated, this closes the last gap by
  hiding the nav link/page for non-admins too.
- app-base.js (byte-identical across the 3 apps): added
  app.util.revealItem() and the --sw-content-offset sticky-positioning
  variable, carried over from the same round of changes in
  sso-manager-node/proxy. Not yet called anywhere in this app -- no
  sticky/reveal use case here yet -- but keeps the shared file in sync.

nodejs/public/css/styles.css

@@ -7,6 +7,12 @@ body {
 	display: flex;
 	flex-direction: column;
 	min-height: 100vh;
+	/* Height of the fixed navbar (plus the update banner, while shown --
+	   see top.ejs's showUpdateBanner/dismissUpdateBanner). Lets an in-page
+	   sticky element offset itself below both fixed elements via
+	   `top: var(--sw-content-offset)` instead of colliding with them at the
+	   viewport's true top:0. */
+	--sw-content-offset: 4.5rem;
 }
 
 #spa-shell {

nodejs/public/lib/js/app-base.js

@@ -584,10 +584,31 @@ app.util = (function(app){
 		document.body.removeChild(element);
 	}
 
+	// Scroll a just-added/-edited element into view and flash its
+	// background, so the user's eye lands on the row that changed instead of
+	// it silently appearing/updating somewhere off-screen. Takes a jQuery
+	// object or a raw DOM node (e.g. jq-repeat's `item.__jq_$el`).
+	function revealItem(el){
+		var node = el && el.jquery ? el[0] : el;
+		if (!node) return;
+		if (typeof node.scrollIntoView === 'function') {
+			node.scrollIntoView({behavior: 'smooth', block: 'center'});
+		}
+		var prevTransition = node.style.transition;
+		var prevBg = node.style.backgroundColor;
+		node.style.transition = 'background-color 1.5s ease';
+		node.style.backgroundColor = 'var(--bs-success-bg-subtle, #d1e7dd)';
+		setTimeout(function(){
+			node.style.backgroundColor = prevBg;
+			setTimeout(function(){ node.style.transition = prevTransition; }, 1500);
+		}, 300);
+	}
+
 	return {
 		downloadFile: downloadFile,
 		getUrlParameter: getUrlParameter,
 		escapeHtml: escapeHtml,
+		revealItem: revealItem,
 	}
 })(app);