fix(news): sort PositiveNewsFeedPanel items by publication date descending

[NewCoder3294]

Summary

• Sorts positive news feed items by publication date descending (newest first) before rendering
• Items with missing or invalid pubDate values are placed at the end of the list
• Sort is applied in renderCards() so it takes effect regardless of the active category filter

Closes #107

Test plan

• Verify that feed items appear with the most recent stories at the top
• Switch between category filters and confirm sort order is maintained
• Confirm items with missing dates appear at the bottom
• Verify share button functionality still works correctly after sorting

🤖 Generated with Claude Code

[vercel]

@NewCoder3294 is attempting to deploy a commit to the Elie Team on Vercel.

A member of the Team first needs to authorize it.