FIX: adjust NFT empty state styling to be consistent with the layout

[GabrielTozatti]

Description

Adjust NFT empty state colors and borders to match the design and maintain consistency with other empty states in the application.

Summary

• Updated colors of NFT empty state to match app standards
• Updated border styling to align with other empty states
• Verified text alignment and spacing remain consistent

Screenshots

Checklist

• I reviewed my PR code before submitting
• I ensured that the implementation is working correctly and did not impact other parts of the app
• I implemented error handling for all actions/requests and verified how they will be displayed in the UI (or there was no error handling needed).
• I mentioned the PR link in the task

[guimroque]

Code Review - Summary

What was done

This PR adjusts the NFT empty state styling to improve consistency with the application's design system. The changes include:

• Updated border color from gradient to solid gray
• Adjusted text colors to use proper gray scale values
• Added font weight to the main text for better hierarchy

Positive Points

• ✅ Small, focused change that addresses a specific styling issue
• ✅ Follows the project's color naming conventions (gray.X format)
• ✅ Improves visual consistency across empty states
• ✅ Good use of semantic color tokens from the theme
• ✅ Maintains proper text hierarchy with font weight adjustment

Issues Found

• 🟡 Minor inconsistency in color naming convention (grey vs gray)
• 🔵 Could benefit from using semantic color tokens for better maintainability

Total comments: 2 (0 critical, 1 important, 1 suggestion)

[aws-amplify-us-east-1]

This pull request is automatically being deployed by Amplify Hosting (learn more).

Access this pull request here: https://pr-798.db1b4e2lqk8yl.amplifyapp.com