Security audit and hardening

## Description
Conduct comprehensive security audit and implement security hardening measures.

## Security Areas to Audit
- [ ] Authentication and authorization
- [ ] Input validation and sanitization
- [ ] Database security and SQL injection prevention
- [ ] API security and rate limiting
- [ ] Agent communication security
- [ ] Data encryption and storage
- [ ] Network security and CORS

## Hardening Tasks
- [ ] Generate strong secrets and keys
- [ ] Implement security headers
- [ ] Add input validation middleware
- [ ] Configure secure CORS policies
- [ ] Implement audit logging
- [ ] Add security monitoring

## Priority: Critical
**Type**: Security
**Component**: All
**Estimated Effort**: 1-2 weeks