[FEATURE] Implement rate limiting #15

📋 Feature Description

Add rate limiting to prevent API abuse and ensure fair usage.

🎯 Feature Type

• Security/Performance

💡 Proposed Solution

• Implement per-IP rate limiting
• Add user-based rate limits
• Configure different limits per endpoint
• Add rate limit headers to responses

✔️ Acceptance Criteria

• Rate limiting middleware implemented
• Configurable limits per endpoint
• Rate limit headers in responses
• 429 status code when limit exceeded
• Documentation updated