feat: reorganize admin panel around accounts

frontend/src/components/admin/AdminSidebar.tsx

@@ -1,7 +1,7 @@
 import { Link, useLocation } from 'react-router-dom'
 import {
   LayoutDashboard,
-  Users,
+  Building2,
   Ticket,
   FileText,
   Gauge,
@@ -17,7 +17,7 @@ import { cn } from '@/lib/utils'
 
 const navItems = [
   { path: '/admin', label: 'Dashboard', icon: LayoutDashboard, end: true },
-  { path: '/admin/users', label: 'Users', icon: Users },
+  { path: '/admin/accounts', label: 'Accounts', icon: Building2 },
   { path: '/admin/invite-codes', label: 'Invite Codes', icon: Ticket },
   { path: '/admin/audit-logs', label: 'Audit Logs', icon: FileText },
   { path: '/admin/plan-limits', label: 'Plan Limits', icon: Gauge },