feat: ST-601-ST-612 M6 polish, beveiliging en launch-ready

- ST-601/602: loading skeletons en error boundary
- ST-603: Sonner toasts op alle CRUD-operaties
- ST-604: DemoTooltip op uitgeschakelde knoppen
- ST-605: KeyboardSensor dnd-kit, Escape sluit modals
- ST-606: min-width banner < 1024px
- ST-607: WCAG AA aria-labels en skip link
- ST-608: rate limiting login (10/min) en registratie (5/uur)
- ST-609: security integratietests cross-user toegang (7 tests)
- ST-610: GitHub Actions CI/CD workflow
- ST-611: README met quickstart, deployment en API-docs
- ST-612: Lars-flow acceptatiechecklist
- fix: settings toont gebruikersnaam i.p.v. interne id
- fix: seed idempotent, testdata altijd gekoppeld aan demo-gebruiker

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

components/dashboard/product-list.tsx

@@ -3,6 +3,7 @@
 import Link from 'next/link'
 import { useRouter } from 'next/navigation'
 import { useTransition } from 'react'
+import { toast } from 'sonner'
 import { Button } from '@/components/ui/button'
 import { restoreProductAction } from '@/actions/products'
 
@@ -25,8 +26,9 @@ export function ProductList({ products, isDemo, showArchived = false }: ProductL
 
   function handleRestore(id: string) {
     startTransition(async () => {
-      await restoreProductAction(id)
-      router.refresh()
+      const result = await restoreProductAction(id)
+      if ('error' in result) toast.error(result.error ?? 'Herstellen mislukt')
+      else { toast.success('Product hersteld'); router.refresh() }
     })
   }