feat(lib-vuetify): add realtime websocket to notification queue

[BatLeDev]

Consolidate the realtime notification queue (proven in data-fair's local fork) into the shared @data-fair/lib-vuetify-events lib so data-fair and portals share one source.

• DfNotificationQueue.vue: subscribe to user:<id>:notifications over WebSocket (@data-fair/lib-vue/ws) and prepend pushed notifications live; refresh(size) reloads the list on menu open and only refreshes the unread count on close.
• eventsUrl prop now means the events service root: REST hits ${eventsUrl}/api/notifications and the WS connects to ${eventsUrl}/api/ (same base as REST, so it reaches the API/ws-server even in split UI/API topologies).
• sender typed as Emitter (adds @data-fair/lib-common-types peer dependency).
• dev.vue passes the new $eventsUrl (service root) instead of $apiPath.
• New e2e test asserts a pushed event appears in the open bell without reload.

Why: the realtime version only lived in data-fair's local fork (which overrode this lib via a vite alias); portals carried a separate static fork. This makes the lib the single canonical source.

Regression risks:

• Breaking prop-contract change: eventsUrl must now be the events service root (not the /api base), and consumers must route /events/api/ to the events service. Verified end-to-end in data-fair and portals — realtime push works through nginx with no extra config.
• New @data-fair/lib-common-types peer dependency; consumers must provide it.
• No version bump in this PR; the 0.3.0 release is a separate follow-up commit on main.