[FEATURE REQUEST] Create Subtasks or Checklists Within Tasks

[SUZ0Y]

User Story
As a daily user who often has complex tasks with multiple steps, I want to be able to create subtasks or checklists within a main task, so that I can break large goals down into manageable pieces and track partial progress without cluttering my main task list.
This makes it easier to stay focused and organized, especially for things like studying, projects, or errands where a single task might have 3–5 small components.

Acceptance Criteria

• Given that I’m creating or editing a task
• When I choose to add subtasks
• Then I should be able to:
• add multiple subtasks/checklist items under the main task
• check off each subtask individually
• see the progress visually (e.g., 2/5 completed)
• mark the main task as complete either manually or automatically once all subtasks are done