fix: replace window.location navigation and remove keyboard focus trap in ShortcutsModal (fixes #4027)

[AMAN194701]

Closes #4027

Description

This PR fixes two issues in ShortcutsModal:

• Replaced window.location.href navigation with router.push() to preserve SPA navigation.
• Removed the forced Tab key focus override that trapped keyboard focus on the close button, allowing normal keyboard navigation within the modal.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature
• Breaking change
• Refactoring
• Documentation update

Verification & Testing

1. Verified shortcut navigation now uses Next.js client-side routing.
2. Confirmed keyboard navigation is no longer trapped on the close button.
3. Ensured no unrelated files or code changes were introduced.

Checklist

• My code follows the style guidelines of this project.
• My changes generate no new warnings or console errors.
• I have performed a self-review of my own code.
• No unrelated files or code changes are included.