- Schema: added due_date and subtasks JSONB columns to tasks
- API: CRUD endpoints for subtasks (/tasks/:id/subtasks)
- API: due date support in create/update task
- TaskDetailPanel: due date picker with overdue/soon badges
- TaskDetailPanel: subtask checklist with progress bar
- TaskPage: full-page task view at /task/HQ-{number}
- Dashboard: task cards link to detail page, show subtask progress & due date badges
- Migration: 0001_mighty_callisto.sql
