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/settings/role-manager.tsx

@@ -1,7 +1,9 @@
 'use client'
 
 import { useState, useTransition } from 'react'
+import { toast } from 'sonner'
 import { Button } from '@/components/ui/button'
+import { DemoTooltip } from '@/components/shared/demo-tooltip'
 import { updateRolesAction } from '@/actions/todos'
 
 const ALL_ROLES = [
@@ -38,8 +40,8 @@ export function RoleManager({ currentRoles, isDemo }: RoleManagerProps) {
     }
     startTransition(async () => {
       const result = await updateRolesAction([...selected])
-      if (result.success) setSaved(true)
-      else setError(result.error ?? 'Opslaan mislukt')
+      if (result.success) { setSaved(true); toast.success('Rollen opgeslagen') }
+      else { setError(result.error ?? 'Opslaan mislukt'); toast.error(result.error ?? 'Opslaan mislukt') }
     })
   }
 
@@ -62,9 +64,9 @@ export function RoleManager({ currentRoles, isDemo }: RoleManagerProps) {
       </div>
       {error && <p className="text-xs text-error">{error}</p>}
       {saved && <p className="text-xs text-success">Rollen opgeslagen.</p>}
-      {!isDemo && (
-        <Button size="sm" onClick={handleSave}>Opslaan</Button>
-      )}
+      <DemoTooltip show={isDemo}>
+        <Button size="sm" onClick={handleSave} disabled={isDemo}>Opslaan</Button>
+      </DemoTooltip>
     </div>
   )
 }