Personal Task Manager Taskie Lightweight to-do app for individuals. Avery Kim Product User enters a title and saves a new task. User marks an existing task as done. The system SHALL let a user create a task with a title. User provides a title The task is saved with status "open". The system SHALL allow marking a task as completed. An open task exists User marks it done Status becomes "completed" with timestamp. The task list SHALL render within 150ms for up to 500 tasks. POST /tasks with title=Buy milk 201 with taskId and status=open