- Add push_subscriptions pgTable with endpoint, p256dh, auth, userId, companyId, deviceLabel
- Add 0055_create_push_subscriptions.sql migration with CREATE TABLE and endpoint index
- Export pushSubscriptions from schema/index.ts
- Create pushService with initVapid, getVapidPublicKey, saveSubscription, removeSubscription, sendPushToAll
- sendPushToAll auto-deletes stale subscriptions on 410/404 response
- Create pushRoutes: GET /vapid-public-key, POST /subscribe, DELETE /subscribe
- Mount /api/push routes and call initVapid() in app.ts with graceful skip
- Install web-push and @types/web-push