Add push notification functionality with tests and digest scheduler

- Implemented push subscription API with tests for subscribing and unsubscribing users.
- Created web push notification tests triggered by child actions.
- Added digest scheduler to send email digests to users at 9 PM local time.
- Developed utility functions for creating and validating digest action tokens.
- Integrated web push sender to handle sending notifications to users.
- Added service worker for handling push notifications in the frontend.
- Created a push opt-in component for user notification preferences.
- Implemented tests for the push opt-in component to ensure correct behavior.
- Updated frontend services to manage push subscriptions and permissions.

frontend/vue-app/src/components/shared/ScrollingList.vue

@@ -206,6 +206,7 @@ onBeforeUnmount(() => {
             props.getItemClass?.(item),
             { 'item-ready': props.readyItemId === item.id },
           ]"
+          :data-item-id="item.id"
           :ref="(el) => (itemRefs[item.id] = el)"
           @click.stop="handleClicked(item)"
         >