Add user profile & dashboard insights

Introduce a user profile page and expand dashboard insights/UI. Added UserController::show and a new users/show view with user stats, domains, tags and groups; updated users index to include a "view profile" link and changed edit form action to /users/{id}/update. Enhanced DashboardController to compute registrar distribution, notification coverage, channel totals and dashboard tag usage; updated dashboard/index.php to show system status, expiring list, registrar/tag widgets and notification coverage panels. Minor controller hardening: DomainController now returns a permission message when a domain is inaccessible, and TagController enforces isolation-mode access checks. UI/JS improvements: add a Quick Actions dropdown in top-nav, refactor dropdown toggle/close logic in layout/base.php, and small notification markup tweak. Routes were adjusted to expose the new user profile endpoints.

app/Controllers/DomainController.php

@@ -531,7 +531,7 @@ class DomainController extends Controller
         }
 
         if (!$domain) {
-            $_SESSION['error'] = 'Domain not found';
+            $_SESSION['error'] = 'You do not have permission to view this domain.';
             $this->redirect('/domains');
             return;
         }