feat(settings): add system diagnostics tool

[Vishvadharman]

## Description

Implemented a System Diagnostics Tool in the Settings tab to help users inspect their TRX environment directly from the TUI.

The new diagnostics popup checks package manager availability, required tools, TRX version, and config file path/status in a formatted table.

Fixes #66

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: opened Settings, selected Run Diagnostics, verified the diagnostics popup renders tool availability, versions, TRX version, and config path.
• cargo test

Additional commands run:

cargo fmt
cargo check

Checklist:

• My code follows the [Coding Guidelines](CONTRIBUTING.md#4-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.

Screenshots (if applicable)

Attached diagnostics popup screenshot.

[vercel]

@Vishvadharman is attempting to deploy a commit to the pie's projects Team on Vercel.

A member of the Team first needs to authorize it.

[pie-314]

@Vishvadharman Go through contribution docs, you have to raise pr in dev branch

[Vishvadharman]

@pie-314 Thanks for pointing that out. I've retargeted the PR to the dev branch and resolved the conflicts. Ready for another review when you have time. 👍

[pie-314]

@Vishvadharman upload a short video of you running the code.
The enter key press is causing conflict since, same key is used for saving the edits in config.