Fix: MediaCard fallback mechanism for broken thumbnails

[anmolgupta2015]

Description

This PR fixes [Issue #333] by improving the fallback mechanism in the MediaCard component when thumbnails fail to load.

🔹 What was the issue?

• If the thumbnailUrl failed to load, the UI displayed a broken image.

🔹 Fix Implemented:

• Now, when the thumbnail fails, it automatically falls back to the main image (item.url).
• Improved error handling to prevent UI glitches.

Changes Made

• Updated MediaCard.tsx:
  ✅ Implemented a thumbnail fallback strategy.
  ✅ Improved error handling for media loading.

How to Test?

1. Run the frontend locally.

2. Verify that the main image is displayed as a fallback instead of a broken thumbnail.

3. Ensure videos and images load correctly in other scenarios.

Screenshots (If Applicable)

### Before

### After

Linked Issues

Closes [#333]

Checklist

✅ Code follows project guidelines.
✅ No breaking changes.
✅ Tested across different scenarios.

[anmolgupta2015]

Hii @Pranav0-0Aggarwal Sir,
Kindly see if my code is good to go...waiting for your feedback.