Set up load testing pipeline with k6 for API and contracts

[Smartdevs17]

Description

No load testing exists. Implement automated load testing with k6 for API endpoints and contract functions.

Acceptance Criteria

• k6 test scenarios for critical API endpoints
• Contract load testing simulation
• CI-integrated load tests with thresholds
• Performance baseline establishment
• Load test report generation
• Scalability bottleneck identification

Technical Scope

• load-tests/
• .github/workflows/
• Edge: CI resource constraints for load testing, test isolation, result reproducibility