feat: add expandable sidebar navigation to settings page

Replace direct SharedProfileSettings rendering with an expandable sidebar
that shows Profile, Security, and Preferences as collapsible sub-items
under Profile & Preferences. Matches the new settings pattern across
all Ciphera frontends.

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

app/settings/page.tsx

@@ -1,4 +1,4 @@
-import ProfileSettings from '@/components/settings/ProfileSettings'
+import SettingsPageClient from './SettingsPageClient'
 
 export const metadata = {
   title: 'Settings - Pulse',
@@ -8,7 +8,7 @@ export const metadata = {
 export default function SettingsPage() {
   return (
     <div className="w-full max-w-6xl mx-auto px-4 sm:px-6 py-8">
-      <ProfileSettings />
+      <SettingsPageClient />
     </div>
   )
 }