Rate Limiting and Security Hardening

[dmccoystephenson]

Implement rate limiting and additional security measures to prevent abuse and attacks.

Acceptance Criteria:

• Add rate limiting library (e.g., Bucket4j)
• Implement rate limits on API endpoints (e.g., 100 req/min)
• Add rate limiting on message sending (e.g., 10 msg/min)
• Implement IP-based rate limiting
• Add CAPTCHA for registration (optional)
• Configure security headers (CSP, HSTS, X-Frame-Options)
• Add input sanitization to prevent XSS
• Implement SQL injection prevention (parameterized queries)
• Add brute force protection for login
• Configure CORS for specific domains only
• Test rate limiting and security measures

Estimated Effort: 4-5 days

Dependencies: TICKET-302 (Production Deployment)