docs: enhance godoc comments, README documentation and add comprehensive AWS deployment guide

[jjacque]

Summary

This PR significantly improves the project documentation:

1. Enhanced Godoc Comments (commit: 0853954)

• Added comprehensive package-level documentation
• Documented all types, structs, and their fields
• Enhanced function and method documentation following Go conventions
• Added clear explanations for interfaces and constants
• Total: 609 lines of well-documented Go code

Key improvements:

• SecretMsgStorer interface with clear contract documentation
• vault struct with detailed field descriptions
• All handlers with parameter, return value, and behavior documentation
• Configuration struct with environment variable mappings
• Token lifecycle and TTL behavior clearly explained

2. Enhanced README.md (commit: e1dff61)

• Expanded from 176 to 480 lines (173% increase)
• Added professional badges (Go version, License, CircleCI)
• Created comprehensive Table of Contents
• Added detailed Features section with emojis
• New API Reference with complete endpoint documentation
• Enhanced Quick Start guide with multiple deployment methods
• Security best practices section
• Development section with project structure
• Improved Contributing guidelines

New sections:

• ✨ Features with 13 key capabilities
• 🚀 Quick Start (Docker Compose + local build)
• 📡 API Reference with curl examples
• 🛠️ Development setup and code quality tools
• �� Security Notice with TLS options

3. Updated Copilot Instructions (commit: 56f8baa)

• Synced with latest repository state
• Updated dependency versions (Go 1.25.1, Vault 1.21.0)
• Added comprehensive Docker build workflow
• Enhanced troubleshooting section
• Added Makefile targets reference

4. Added golangci-lint Configuration (commit: 84e6293)

• Created .golangci.yml with concurrency limit of 2
• Prevents resource exhaustion in CI environments
• 5-minute timeout for analysis
• Resolves CircleCI lint job failures

5. Added AWS Deployment Guide (commit: 383f6a9)

• NEW: Comprehensive 705-line AWS deployment documentation
• Added AWS_DEPLOYMENT.md with three deployment options:
  • ECS with Fargate (recommended)
  • EKS (Kubernetes)
  • EC2 with Docker
• Complete infrastructure setup instructions with Terraform examples
• Security considerations and best practices
• Cost optimization tips
• Updated README.md with link to AWS deployment guide

Testing

• ✅ All files compile successfully
• ✅ Code passes gofmt formatting
• ✅ Passes go vet static analysis
• ✅ All tests pass
• ✅ golangci-lint passes with new configuration

Impact

• Better developer onboarding experience
• Clearer API documentation
• Improved code maintainability
• Professional, comprehensive README
• Production-ready AWS deployment documentation
• Fixed CI/CD pipeline issues

[eranchetz]

Left one comment otherwise LGTM

[jjacque]

@eranchetz i also cherry-picked your commit about AWS deployment instructions (644ebaf) from #127