Implement API Rate Limiting to Prevent Abuse

[Fatimasanusi]

Description:
To prevent API exhaustion and avoid hitting rate limits from our blockchain node providers when analyzing high-volume contracts, we must implement defensive backend architecture.

Acceptance Criteria:

• Implement a token-bucket rate limiter middleware for incoming client HTTP requests.
• Add circuit breakers to third-party RPC connections so the application gracefully degrades if a node provider goes down.
• Ensure the API returns standard 429 Too Many Requests responses when client thresholds are exceeded.

[Fabluchy]

I’m interested in this task because API security and reliability are important for building scalable systems. I’d like to contribute by implementing rate limiting to prevent abuse and ensure stable, secure API usage. I'll submit a PR within 24 hours.