Fix: Consistent button styling

[Alvi24-hub]

📝 Description

Standardized button styling across all project modals with consistent green glow design system. Removed redundant inline button styles and centralized them in styles.css.

🔗 Linked Issue

Closes #1176

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📋 Contribution Checklist

• My code strictly adheres to the project guidelines (Standard library only, procedural code, clean spacing).
• I have verified that my files are placed in the correct directory.
• I have tested my changes thoroughly on my local machine.
• I have included interactive emojis and clean console/UI outputs.
• GSSoC 2026: I have been formally assigned to this issue and noted it above.

[vercel]

@Alvi24-hub is attempting to deploy a commit to the Anuj's projects Team on Vercel.

A member of the Team first needs to authorize it.

[github-actions]

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