fix: add shadows to feature cards in dark mode

[Gunjan10-droid]

Related Issue

Fixes #159

Description

In dark mode, the "Why Choose LearnHub" feature cards didn’t have shadows, making them blend into the background.
This PR adds subtle shadows in dark mode to improve readability, visual hierarchy, and consistency with light mode design.

Fixes # (issue number)

Type of PR

• Feature enhancement

Screenshots / videos (if applicable)

Before:

After:

Before:

After:

Checklist:

• I have made this change from my own.
• I have mentioned the issue number in my Pull Request.
• I have gone through the CONTRIBUTING.md file before contributing
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have tested the changes thoroughly before submitting this pull request.
• I have provided relevant issue numbers and screenshots after making the changes.

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[github-actions]

Thank you for submitting your pull request! 🙌 We'll review it as soon as possible.). If there are any specific instructions or feedback regarding your PR, we'll provide them here. Thanks again for your contribution! 😊

[netlify]

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Project	Deployment	Preview	Comments	Updated (UTC)
learn-hub	Ready	Preview	Comment	Aug 20, 2025 5:31pm

[github-actions]

🎉🎉 Thank you for your contribution! Your PR #221 has been merged! 🎉🎉