API rate limiting 🔄

### The issue ⚡ There is no API rate limiting implementation in place which puts the API endpoints at risk of abuse, i.e. DDOS. ### Suggested improvements 🔨 Add rate limiting to protect the API endpoints against illegitimate use and abuse. ### References 🔗 https://unkey.dev/docs/features/ratelimiting https://github.com/upstash/ratelimit