feat: follow-ups, reminders, and a due-this-week inbox

[leobrqz]

Summary

Introduce lightweight tasks tied to an application and/or an appointment, with optional due dates and types (e.g. check-in, prep). Surface items due soon in a dedicated inbox view and optionally on the dashboard.

The calendar reflects scheduled events but not asynchronous obligations (send thank-you, ping recruiter, prepare take-home). A small task layer closes that gap without replacing the calendar.

Proposed behavior

• Create, edit, complete, and dismiss follow-ups from application context and from appointment context where relevant.
• Fields include title or template, due date (optional), link to parent application or appointment, and status (open, done, snoozed if you include snooze).
• “Inbox” or “Due this week” aggregates open items with due dates in the current window; empty and overdue states are obvious.
• Completed items remain accessible for a sensible period or archive rule (product decision) so history is not lost.

Scope notes

• Notifications (email/push) are out of scope unless explicitly added later; the feature remains valuable as in-app lists and due sorting.
• Avoid duplicating full calendar semantics; appointments stay the source of truth for timed events.

Success criteria

• User can see all upcoming follow-ups in one place.
• Creating a follow-up from an application is discoverable and fast.
• Completing an item removes it from the active inbox without breaking links to the parent record.