feat: added new system

[imriadutta]

Description

This PR added a task-management flow named Mind Queue, a minimalist productivity app.

Summary of changes

• Added deep cloning for systems and tasks to prevent shared references.

• Improved validation and error handling when creating or renaming systems, headers, and tasks.

• Introduced confirmation dialogs for destructive actions (system, header, and task deletion).

• Enhanced task management with:

  • Clone task functionality
  • Move task up/down within a header
  • Inline edit via tap and extended actions via long-press

• Improved UX consistency by centralizing dialog handling and refreshing views after state changes.

• Ensured all state changes are persisted immediately to data.json.

This makes the app more robust against accidental data loss and improves usability for larger task trees.

No breaking changes were introduced.

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Test Code

Manual testing performed locally:

• Create, rename, clone, and delete systems

• Add, rename, and delete headers

• Add, edit, clone, move, toggle, and delete tasks

• Verified data persistence across app restarts

• Tested edge cases:

  • Prevent deleting the last remaining system
  • Prevent duplicate system/header names
  • Prevent empty inputs

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Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality not to work as expected)
• This change requires a documentation update

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Checklist

• I signed the CLA.
• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings
• New and existing tests pass locally with my changes
• I have made corresponding changes to the documentation (not required for this change)

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Additional details

• All dialogs are managed via a shared overlay to avoid stacking or UI lockups.
• No schema changes were made to data.json; existing user data remains compatible.
• Code structure remains single-file for now to align with the current project scope.

Summary by Sourcery

Add a new Flet-based "Mind Queue" example app for task management with persistent local storage.

New Features:

• Introduce the Mind Queue task management app with systems, headers, and tasks hierarchy.
• Support creating, renaming, cloning, and deleting systems with validation and confirmation dialogs.
• Add header management within a system, including creation, renaming, and deletion with safeguards.
• Enable task CRUD operations, completion toggling, cloning, reordering, and inline editing via tap/long-press actions.
• Persist all Mind Queue state changes immediately to a local JSON data file.

Enhancements:

• Standardize dialog handling for confirmations and edits to improve UX consistency in the Mind Queue app.

Documentation:

• Add README documentation describing Mind Queue features, data model, usage instructions, and future enhancements.

[sourcery-ai]

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