Sprint: pbi-55 (#156)

* ST-cmovs79lt: Schema + migratie PushSubscription model

Voeg PushSubscription model toe aan prisma/schema.prisma met
snake_case-conventie, relation field op User, en bijbehorende
migratie (push_subscriptions tabel, FK + index op user_id).

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

* ST-cmovs7e3o: web-push dependency + VAPID env vars feature-gated

Voeg web-push + @types/web-push toe aan package.json.
Registreer NEXT_PUBLIC_VAPID_PUBLIC_KEY, VAPID_PRIVATE_KEY,
VAPID_SUBJECT en INTERNAL_PUSH_SECRET als .optional() in lib/env.ts.
Documenteer alle vier in .env.example en README.

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

* ST-cmovs7jgr: lib/push-server.ts met sendPushToUser + stale-cleanup

Server-only push-lib met VAPID feature-gate, send naar alle
subscriptions van een user, en automatische cleanup bij 404/410.
Unit tests: success-pad, 410 verwijdert sub, 404 verwijdert sub,
andere errors loggen zonder delete.

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

* ST-cmovs7ouz: lib/push-client.ts client-side push helpers + stub actions/push.ts

Client-side helpers: isPushSupported, isIOSSafari, isStandalonePWA,
urlBase64ToUint8Array, subscribeToPush, unsubscribeFromPush.
Stub actions/push.ts zodat imports resolven (implementatie volgt
in volgende taak). Unit tests voor urlBase64ToUint8Array.

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

* ST-cmovs7ut4: actions/push.ts subscribeToPushAction + unsubscribeFromPushAction

Vervangt stub met volledige implementatie: requireUser via getSession,
demo-block, Zod-validatie, upsert met user_id-scoping en user-scoped
deleteMany. Tests (8): idempotentie, demo-block, unauthenticated, invalid input.

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

* ST-cmovs80c1: POST /api/internal/push/send met constant-time Bearer check

Route: 503 als INTERNAL_PUSH_SECRET uitstaat, 401 bij verkeerd secret
(timingSafeEqual), 400 bij invalid JSON, 422 bij Zod-fout, 204 bij succes.
push-server.ts: env-import vervangen door process.env om SESSION_SECRET
validatie tijdens build te omzeilen. Tests aangepast.

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

* ST-cmovs862j: Admin test-send route + public/sw.js service worker

POST /api/internal/push/test-send: requireAdmin check (redirect bij
niet-admin), optioneel body met defaults, roept sendPushToUser aan, 204.
public/sw.js: push-handler met showNotification, notificationclick met
same-origin guard, focus bestaand venster of openWindow.

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

* ST-cmovs8jvq: PushToggle component met 3 states + iOS-banner

Client component met states loading/unsupported/ios-needs-install/
denied/subscribed/unsubscribed. useEffect detecteert initial status,
permission-prompt alleen via user-click. iOS-banner NL, denied-uitleg,
subscribe/unsubscribe knoppen met sonner-toasts.

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

* ST-cmovs8psg: notifications-sheet + iOS meta-tags in layout

notifications-sheet.tsx: PushToggle onderin met sectie
'Notificatie-instellingen' en visuele scheidslijn.
app/layout.tsx: appleWebApp.capable, statusBarStyle en
mobile-web-app-capable meta-tags toegevoegd via Next.js Metadata API.
manifest.json had al display: standalone.

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

* ST-cmovs8vxj: docs/patterns/web-push.md pattern-documentatie

Architectuur-diagram, payload-shape, foutcodes, VAPID-config,
iOS-quirks, demo-users blokkade, trigger-voorbeelden (server +
HTTP) en admin-testroute curl-voorbeeld.

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

---------

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

public/sw.js

@@ -0,0 +1,42 @@
+// Service Worker for Web Push notifications (PBI-55)
+
+self.addEventListener('push', (event) => {
+  let payload = { title: 'Scrum4Me', body: '', url: '/', tag: undefined }
+  try {
+    if (event.data) payload = { ...payload, ...event.data.json() }
+  } catch (_) {}
+
+  event.waitUntil(
+    self.registration.showNotification(payload.title, {
+      body: payload.body,
+      icon: '/icon-192.png',
+      badge: '/icon-192.png',
+      tag: payload.tag,
+      data: { url: payload.url },
+    })
+  )
+})
+
+self.addEventListener('notificationclick', (event) => {
+  event.notification.close()
+
+  const rawUrl = event.notification.data?.url || '/'
+  const targetUrl = new URL(rawUrl, self.location.origin)
+
+  // Same-origin guard
+  if (targetUrl.origin !== self.location.origin) return
+
+  event.waitUntil(
+    self.clients
+      .matchAll({ type: 'window', includeUncontrolled: true })
+      .then((clients) => {
+        for (const client of clients) {
+          if (client.url.startsWith(self.location.origin) && 'focus' in client) {
+            client.navigate(targetUrl.href)
+            return client.focus()
+          }
+        }
+        return self.clients.openWindow(targetUrl.href)
+      })
+  )
+})