Generate dashboard reminders from waiting follow-up dates

[alexeygrigorev]

Context

The live Operations Home now shows waiting tasks and follow-up metadata from work-engine tasks, and the backend supports status=waiting, waitingFor, and followUpAt. The next step is to turn those fields into first-class reminders instead of relying only on dashboard filtering.

Related: #10, #48.

Acceptance Criteria

• Waiting tasks with followUpAt <= now create or surface a follow-up-due reminder.
• Follow-up reminders are visible on the Operations Home without hiding the underlying task/workflow risk.
• Future waiting tasks remain visible as waiting/tracked work but do not outrank due follow-ups.
• Operator can resolve a follow-up by either moving the task back to todo or setting a next followUpAt.
• Reminder behavior is covered by backend tests and frontend model/rendering tests.

Notes

This should build on the waiting task state added in commit d981f47 and avoid a separate reminder-only tool.

[alexeygrigorev]

Implemented in 247a994 and deployed successfully in https://github.com/DataTalksClub/dataops/actions/runs/28293227669.

What shipped:

• GET /api/notifications now generates due follow-up reminders from waiting tasks before returning notifications.
• Reminder generation is idempotent per taskId + followUpAt, including dismissed reminders, so dismissing does not recreate the same reminder immediately.
• Updating a waiting task to a new due followUpAt can create a new reminder.
• Follow-up reminders include type=follow-up-due, taskId, bundleId, and dueAt.
• Work-engine dashboard now includes due waiting tasks in the daily task table and marks them with a waiting/follow-up badge.
• Portable notification export now includes notification_type as well as existing task_id and due_at.

Verification:

• NODE_ENV=test SKIP_AUTH=true node --import tsx --test tests/notifications.test.ts tests/home-dashboard.test.ts tests/export-portable.test.ts - 73 passed
• npm test in work-engine - 604 passed
• npm run typecheck in work-engine
• CI/CD deploy run passed, including private work-engine smoke test

Closing this issue because the V1 reminder-generation slice described here is implemented. Remaining richer actions such as inline response-received / next-follow-up controls should continue under the broader dashboard/workflow action issues.

[alexeygrigorev]

Implemented and deployed in 247a994. Follow-up action controls remain part of the broader V1 dashboard/workflow work.