URL Shortener API

POST /api/shorten  JSON: {"long_url":"https://..."}
GET  /api/shorten?long_url=https://...  (Browser friendly)
GET  /s/{code}   -> 301 redirect
GET  /health      -> Health check
GET  /debug       -> Debug info

Example: https://yourdomain.com/api/shorten?long_url=https://google.com