feat: add multi-column package list sorting (Name, Version, Provider)

[vaishnavi003-svg]

Description

Adds multi-column package list sorting feature. Users can now sort packages by Name, Version, or Provider using keyboard shortcuts.

Fixes #70

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 to not work as expected)
• Documentation update

How Has This Been Tested?

• Manual test (please describe)

Tested with:

1. Press s to open sort menu
2. Press n → packages sorted by Name
3. Press v → packages sorted by Version
4. Press p → packages sorted by Provider
5. Sort indicator shows in list header: "Packages (X) (sorted by: Name)"

• cargo test

Checklist:

• My code follows the Coding Guidelines.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have NOT added useless AI-generated comments.
• I have NOT deleted existing unrelated comments.
• I have NOT modified files unrelated to this task.
• I have included screenshots/recordings (for UI changes).
• My changes generate no new warnings (clippy/fmt).
• I have linked the issue I am working on.

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[vaishnavi003-svg]

@pie-314
ready to review.
thank you