feat: restructure sidebar hierarchy and add full audit view

Reorganize the sidebar into a proper hierarchy (Overview, Full Audit,
Namespaces) and add a Full Audit dashboard view that includes skipped
checks. Namespace routes move to /polaris/ns/:namespace to avoid
path collisions, and namespace detail pages now link out to the
Polaris dashboard.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/components/DynamicSidebarRegistrar.tsx

@@ -16,10 +16,10 @@ export default function DynamicSidebarRegistrar() {
       if (registeredNamespaces.has(ns)) continue;
       registeredNamespaces.add(ns);
       registerSidebarEntry({
-        parent: 'polaris',
+        parent: 'polaris-namespaces',
         name: `polaris-ns-${ns}`,
         label: ns,
-        url: `/polaris/${ns}`,
+        url: `/polaris/ns/${ns}`,
         icon: 'mdi:folder-outline',
       });
     }