Revamp admin dashboard analytics and UI

Refactored the admin dashboard to use tabbed navigation for analytics and management. Enhanced AdminAnalytics with Recharts visualizations, added top vendors by revenue, and improved chart tooltips. Removed unused columns from vendor table. Updated layout and notification context to exclude admin pages from dashboard-specific UI and notifications. Minor debug logging added to SystemStatusCard.

components/layout/layout.tsx

@@ -18,6 +18,8 @@ export default function Layout({ children }: LayoutProps) {
   
   // Check if we're in a chat detail page
   const isChatDetailPage = pathname?.includes('/dashboard/chats/') && !pathname?.endsWith('/chats') && !pathname?.endsWith('/new')
+  // Check if we're on an admin page
+  const isAdminPage = pathname?.includes('/dashboard/admin')
 
   useEffect(() => setMounted(true), [])
 
@@ -27,7 +29,7 @@ export default function Layout({ children }: LayoutProps) {
     <div className={`flex h-screen ${theme === "dark" ? "dark" : ""}`}>
       <Sidebar />
       <div className="w-full flex flex-1 flex-col">
-        {!isChatDetailPage && (
+        {!isChatDetailPage && !isAdminPage && (
           <header className="h-16 border-b border-border flex items-center justify-end px-6">
             <div className="flex items-center space-x-2">
               <UnifiedNotifications />