A tiny URL shortener — re-platformed from OSS onto a Cloudflare Worker.
POST /shortener {"url":"https://…"} → 201 {"key","url","short_url"}
GET /{key} → 302 redirect to the URL | 404
GET /shortener/{key} → 200 {"key","url"} | 404 (JSON, no redirect)
GET /health → 200 {"ok":true}