feat: Go Project Setup and Architecture (#2)

[starbops]

Summary

Implements issue #2: Go Project Setup and Architecture

This PR establishes the foundational Go project structure for VoidRunner with:

• Go Module & Dependencies: Gin web framework, structured logging, CORS, testing libraries
• Project Architecture: Standard Go layout following CLAUDE.md guidelines
• Configuration Management: Environment variable support with sensible defaults
• HTTP Server: Gin-based API with essential middleware stack
• Health Endpoints: /health and /ready for monitoring
• Security: Security headers, CORS, error handling, non-root Docker execution
• Observability: Structured JSON logging with request correlation and duration tracking
• Testing: Comprehensive test suite with 65-89% coverage
• Docker: Multi-stage build with security best practices
• Documentation: Updated README with setup instructions

Technical Details

Architecture Components

• Middleware Stack: Request ID, CORS, Security Headers, Logging, Recovery, Error Handling
• Health Checks: Kubernetes-ready health and readiness endpoints
• Configuration: Optional .env file with environment variable defaults
• Logging: slog-based structured logging with request correlation
• Security: Security headers, input validation, safe type assertions

Quality Assurance

• ✅ All tests passing (handlers, middleware, configuration)
• ✅ No credential leaks or hardcoded secrets
• ✅ Clean codebase with no temporary debug code
• ✅ Follows conventional commit standards
• ✅ Docker builds successfully with health checks
• ✅ Application starts with or without .env file

Test Plan

• Application builds and runs locally
• Health endpoints return proper responses
• All middleware functions correctly
• Configuration loads from environment variables
• Docker container builds and health checks pass
• Test suite achieves target coverage

Breaking Changes

None - this is the initial implementation.

Related Issues

Closes #2
Part of Epic #1: Core API Infrastructure

🤖 Generated with Claude Code

[starbops]

Superseded by #34