feat(ST-111ci8t4): /admin/users pagina met tabel, role-editor en delete-dialog

- app/(app)/admin/layout.tsx: admin-sidebar met links (Gebruikers/Claude Jobs/Producten)
- app/(app)/admin/page.tsx: redirect naar /admin/users
- app/(app)/admin/users/page.tsx: server component, query users+roles, geeft userId door
- components/admin/users-table.tsx: client component met UsersTable, RoleBadge,
  RolesDialog (checkboxes, eigen ADMIN-rol geblokkeerd), DeleteDialog (confirm),
  ResetToggle — alles via useTransition + server actions

app/(app)/admin/layout.tsx

@@ -0,0 +1,16 @@
+import { requireAdmin } from '@/lib/auth-guard'
+import Link from 'next/link'
+
+export default async function AdminLayout({ children }: { children: React.ReactNode }) {
+  await requireAdmin()
+  return (
+    <div className="flex min-h-screen">
+      <nav className="w-48 border-r p-4 flex flex-col gap-2">
+        <Link href="/admin/users" className="text-sm font-medium text-foreground hover:text-primary">Gebruikers</Link>
+        <Link href="/admin/jobs" className="text-sm font-medium text-foreground hover:text-primary">Claude Jobs</Link>
+        <Link href="/admin/products" className="text-sm font-medium text-foreground hover:text-primary">Producten</Link>
+      </nav>
+      <main className="flex-1 p-6">{children}</main>
+    </div>
+  )
+}

app/(app)/admin/page.tsx

@@ -0,0 +1,5 @@
+import { redirect } from 'next/navigation'
+
+export default function AdminPage() {
+  redirect('/admin/users')
+}

app/(app)/admin/users/page.tsx

@@ -0,0 +1,19 @@
+import { requireAdmin } from '@/lib/auth-guard'
+import { prisma } from '@/lib/prisma'
+import { UsersTable } from '@/components/admin/users-table'
+
+export default async function AdminUsersPage() {
+  const session = await requireAdmin()
+
+  const users = await prisma.user.findMany({
+    include: { roles: { select: { role: true } } },
+    orderBy: { created_at: 'desc' },
+  })
+
+  return (
+    <div className="space-y-4">
+      <h1 className="text-xl font-semibold text-foreground">Gebruikers</h1>
+      <UsersTable users={users} currentUserId={session.userId} />
+    </div>
+  )
+}