Implement comprehensive test suite

## Description
Add comprehensive testing to ensure code quality and reliability.

## Tasks
- [ ] Unit tests for Go API (80%+ coverage)
- [ ] Unit tests for Python enrichment service
- [ ] Unit tests for React components
- [ ] Integration tests for API endpoints
- [ ] End-to-end tests for critical user flows
- [ ] Performance tests for high-load scenarios
- [ ] Security tests for authentication and authorization

## Acceptance Criteria
- [ ] All new code has corresponding tests
- [ ] Test coverage exceeds 80%
- [ ] All tests pass in CI/CD pipeline
- [ ] Performance benchmarks are established

## Priority: High
**Type**: Feature
**Component**: Testing
**Estimated Effort**: 2-3 weeks