Add database maintenance tooling

- Implement maintenance hooks (useMaintenanceTables, useVacuumTable, useAnalyzeTable, useReindexTable)
- Add DatabaseMaintenance page and UI for vacuum/analyze/reindex
- Wire new route / admin/database-maintenance and sidebar entry
- Remove DatabaseMaintenance icon usage on page and align with AdminLayout props

src/components/layout/AdminSidebar.tsx

@@ -1,4 +1,4 @@
-import { LayoutDashboard, FileText, Flag, Users, Settings, ArrowLeft, ScrollText, BookOpen, Inbox, Mail, AlertTriangle, Shield, Activity, BarChart } from 'lucide-react';
+import { LayoutDashboard, FileText, Flag, Users, Settings, ArrowLeft, ScrollText, BookOpen, Inbox, Mail, AlertTriangle, Shield, Activity, BarChart, Database } from 'lucide-react';
 import { NavLink } from 'react-router-dom';
 import { useUserRole } from '@/hooks/useUserRole';
 import { useSidebar } from '@/hooks/useSidebar';
@@ -73,6 +73,12 @@ export function AdminSidebar() {
       url: '/admin/database-stats',
       icon: BarChart,
     },
+    {
+      title: 'Database Maintenance',
+      url: '/admin/database-maintenance',
+      icon: Database,
+      visible: isSuperuser, // Only superusers can access
+    },
     {
       title: 'Users',
       url: '/admin/users',
@@ -134,7 +140,7 @@ export function AdminSidebar() {
           <SidebarGroupLabel>Navigation</SidebarGroupLabel>
           <SidebarGroupContent>
             <SidebarMenu>
-              {navItems.map((item) => (
+              {navItems.filter(item => item.visible !== false).map((item) => (
                 <SidebarMenuItem key={item.url}>
                   <SidebarMenuButton asChild tooltip={collapsed ? item.title : undefined}>
                     <NavLink