- AdminSidebar: removed dropdown menu, flat nav links, no scrolling
- Removed SETTINGS_SUB_LINKS array
- Removed settingsOpen state and dropdown logic
- Settings is now a simple link to /admin/settings
- Nav uses overflow-hidden to prevent sidebar scroll
- SettingsClient: unified tabbed interface (like CommunicationsPage)
- New tabs: General, Add-ons, Billing, Integrations, AI, Advanced
- Uses AdminFilterTabs for navigation
- Each tab shows a card with link to full settings page
- Redirected pages to /admin/settings#tab:
- /admin/settings/apps → /admin/settings#addons
- /admin/settings/integrations → /admin/settings#integrations
- /admin/settings/ai → /admin/settings#ai
- /admin/advanced → /admin/settings#advanced
All TypeScript checks pass.