Implement admin database stats dashboard

Add admin-only database statistics dashboard
- Introduces types for database statistics and recent additions
- Implements hooks to fetch statistics and recent additions via RPCs
- Adds UI components for stats cards and a recent additions table
- Integrates new AdminDatabaseStats page and routing under /admin/database-stats
- Updates admin sidebar and app routes to expose the new dashboard
- Enables real-time updates and export capabilities for recent additions

src/components/layout/AdminSidebar.tsx

@@ -1,4 +1,4 @@
-import { LayoutDashboard, FileText, Flag, Users, Settings, ArrowLeft, ScrollText, BookOpen, Inbox, Mail, AlertTriangle, Shield, Activity } from 'lucide-react';
+import { LayoutDashboard, FileText, Flag, Users, Settings, ArrowLeft, ScrollText, BookOpen, Inbox, Mail, AlertTriangle, Shield, Activity, BarChart } from 'lucide-react';
 import { NavLink } from 'react-router-dom';
 import { useUserRole } from '@/hooks/useUserRole';
 import { useSidebar } from '@/hooks/useSidebar';
@@ -68,6 +68,11 @@ export function AdminSidebar() {
       url: '/admin/rate-limit-metrics',
       icon: Shield,
     },
+    {
+      title: 'Database Stats',
+      url: '/admin/database-stats',
+      icon: BarChart,
+    },
     {
       title: 'Users',
       url: '/admin/users',