feat: ST-006-ST-008 auth pages, middleware, nav shell en dashboard

- Login/register pages met AuthForm (useActionState + useFormStatus)
- Server Actions voor login, register, logout met Zod validatie
- Middleware checkt session cookie zonder iron-session op Edge runtime
- AppLayout met auth-check en NavBar met demo badge en actieve links
- Dashboard toont productenlijst via ProductList Client Component
- Fix: a-in-a hydration error opgelost door div plus useRouter te gebruiken

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

app/(auth)/login/page.tsx

@@ -0,0 +1,40 @@
+import Link from 'next/link'
+import { loginAction } from '@/actions/auth'
+import { Button } from '@/components/ui/button'
+import { Input } from '@/components/ui/input'
+import { AuthForm } from '@/components/auth/auth-form'
+
+export default function LoginPage() {
+  return (
+    <div className="min-h-screen bg-background flex items-center justify-center p-4">
+      <div className="w-full max-w-sm space-y-6">
+
+        {/* Logo / titel */}
+        <div className="text-center space-y-1">
+          <h1 className="text-2xl font-medium text-foreground">Scrum4Me</h1>
+          <p className="text-sm text-muted-foreground">Inloggen bij je account</p>
+        </div>
+
+        {/* Formulier */}
+        <div className="bg-surface-container-low rounded-xl p-6 space-y-4 border border-border">
+          <AuthForm action={loginAction} submitLabel="Inloggen" />
+
+          <div className="text-center text-sm text-muted-foreground">
+            Nog geen account?{' '}
+            <Link href="/register" className="text-primary hover:underline font-medium">
+              Registreer hier
+            </Link>
+          </div>
+        </div>
+
+        {/* Demo credentials */}
+        <div className="bg-info-container text-info-container-foreground rounded-xl p-4 text-sm space-y-1 border border-border">
+          <p className="font-medium">Demo-account (alleen lezen)</p>
+          <p>Gebruikersnaam: <span className="font-mono font-medium">demo</span></p>
+          <p>Wachtwoord: <span className="font-mono font-medium">demo1234</span></p>
+        </div>
+
+      </div>
+    </div>
+  )
+}

app/(auth)/register/page.tsx

@@ -0,0 +1,31 @@
+import Link from 'next/link'
+import { registerAction } from '@/actions/auth'
+import { AuthForm } from '@/components/auth/auth-form'
+
+export default function RegisterPage() {
+  return (
+    <div className="min-h-screen bg-background flex items-center justify-center p-4">
+      <div className="w-full max-w-sm space-y-6">
+
+        {/* Logo / titel */}
+        <div className="text-center space-y-1">
+          <h1 className="text-2xl font-medium text-foreground">Scrum4Me</h1>
+          <p className="text-sm text-muted-foreground">Nieuw account aanmaken</p>
+        </div>
+
+        {/* Formulier */}
+        <div className="bg-surface-container-low rounded-xl p-6 space-y-4 border border-border">
+          <AuthForm action={registerAction} submitLabel="Account aanmaken" />
+
+          <div className="text-center text-sm text-muted-foreground">
+            Al een account?{' '}
+            <Link href="/login" className="text-primary hover:underline font-medium">
+              Inloggen
+            </Link>
+          </div>
+        </div>
+
+      </div>
+    </div>
+  )
+}