Feat/help tab hint

[vaishnavi003-svg]

Description

Adds keyboard shortcut hints for Tab (next tab) and Shift+Tab (previous tab) in the help menu to improve discoverability for new users.

Fixes #114

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 by:

1. Running cargo run
2. Pressing ? key to open help menu
3. Verified "Tab → Next tab" and "Shift+Tab → Previous tab" appear in the Navigation section
4. Verified Tab and Shift+Tab shortcuts work as expected

• 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. (N/A - simple text addition)
• 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). (Can add if required)
• 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
PR has been recreated with base dev branch as requested.