Add Longevity World Cup

[nopara73]

Adds Longevity World Cup to the Miscellaneous healthcare datasets section.

Why it fits:

• It exposes public biological-age leaderboard and athlete profile data.
• The data is available through JSON endpoints suitable for research/exploration.
• The endpoint includes CORS support for programmatic use.

Validation:

• Confirmed https://longevityworldcup.com/api/data/athletes returns HTTP 200.
• Confirmed response content type is JSON and Access-Control-Allow-Origin is *.