feat: long-term load testing infrastructure

[wenfix]

Description

This PR implements infrastructure-agnostic improvements to the load testing system that can be completed before DevOps involvement. All functionality works locally and is designed with abstraction layers ready for AWS integration.

• ADDED:

  • Environment configuration system supporting dev/UAT/prod environments via environment variables or config file (ready for AWS Secrets Manager integration)
  • Result uploader abstraction with local file system implementation (S3-ready interface)
  • Metadata collection for test results (runner type detection, git SHA, container ID)
  • --environment CLI option to auto-resolve relay URLs from configuration
  • Docker support: Dockerfile, build scripts, and container detection
  • GitHub Actions workflows: load test workflow with manual dispatch and production approval, Docker image build workflow
  • Comprehensive documentation in README with usage examples
  • Local workflow testing script for simulating GitHub Actions locally
  • Example environment configuration file

• CHANGED:

  • Enhanced CLI to support environment-based configuration alongside explicit target URLs
  • Extended TestResults type with metadata fields (environment, gitSha, runnerType, containerId)
  • Improved error handling and validation for environment configuration

Key Features

• Fully testable locally: All functionality works without AWS infrastructure
• Abstraction layers: Ready for AWS Secrets Manager and S3 integration without code changes
• Production safety: Manual approval required for production environment in GitHub Actions
• Platform-aware: Works on macOS, Linux, and in Docker containers

Testing

All functionality has been tested locally:

• ✅ Direct CLI usage with explicit targets
• ✅ Environment-based configuration (env vars and config file)
• ✅ Both test scenarios (connection-storm, steady-state)
• ✅ Docker container execution
• ✅ Local workflow script
• ✅ Error handling and validation
• ✅ Result generation with metadata

Next Steps

After DevOps sets up AWS infrastructure:

• Implement AWS Secrets Manager integration for environment URLs
• Implement S3 uploader for result storage
• Update GitHub Actions workflow to use ECS/EC2/Lambda
• Add CloudWatch integration for logging and metrics

Checklist

• Tests are included if applicable
• Any added code is fully documented