Refactor: migrate Jekyll-based shortlink pages to Cloudflare Worker + links.json

[elvisdragonmao]

This PR replaces the existing GitHub Pages + Jekyll + Markdown redirect pages implementation with a significantly simpler, more maintainable, and faster Cloudflare Worker + links.json based shortlink system.

The new architecture removes all static-site generation overhead, eliminates the need for JavaScript-based delayed redirects, and allows SITCON shortlinks to be managed through a single JSON file with clean git history and instant edge deployment.

• Much simpler layout and less file. One JSON to rule them all.
• Code is simple af.
• Much faster, no delay like 2 sec.
• 301 won't remove referer.
• Better SEO, keeps all og title, description, image.
• No more Jekyll Pages build delay.
• No more JS redirect.
• Instant redirect on Cloudflare edge.