Add `fetchJobTasks` operation to the Jobs API. This returns a summary of
each of the job's tasks, suitable for display in a task list view.
The actually used fields may need tweaking once we actually have a task
list view, but at least the functionality is there.
Replace the Vue v2 webapp with a Vue v3 one, and embed the OpenAPI
client in the webapp itself (instead of being its own npm project).
- Vue v2.x -> v3.x
- Tabulator v4.x -> v5.1
- Moment JS -> replaced with Luxon JS
- Vue CLI/UI -> replaced with Vite
