feat: adds fetch mcp server

[ChrisJBurns]

Summary

This PR adds a complete Go implementation of the fetch MCP server with SSE transport, comprehensive testing, and modern development tooling. This implementation provides the same functionality as the original Python MCP fetch server but with significant performance and security improvements.

🚀 Key Features

Core Implementation

• SSE-based MCP Server: Uses Server-Sent Events instead of stdio for better client compatibility
• Web Content Fetching: Retrieves URLs and extracts textual content with HTML-to-markdown conversion
• Robots.txt Compliance: Respects robots.txt rules (configurable)
• Content Processing: Uses readability algorithms to extract main content from web pages
• Configurable Options: Supports custom user agents, proxy settings, and content formatting

Architecture & Code Quality

• Modern Go Project Structure: Follows standard cmd/ and pkg/ organization
• Comprehensive Testing: 100% test coverage across all packages with mock servers
• Lint Compliance: Passes all golangci-lint rules with package documentation
• Type Safety: Fully typed with proper error handling throughout

Task Automation

• Taskfile.yml: Comprehensive task automation for build, test, lint, and development
• Local Development: Easy setup with task build, task run, task test
• Code Quality: Automated formatting and linting with task fmt and task lint

GitHub Actions Workflows

• Build Pipeline: Automated building and testing on PRs and main
• Lint Pipeline: Code quality checks with golangci-lint
• Test Pipeline: Comprehensive test execution
• Release Pipeline: Automated releases with semantic versioning
• Container Build: Multi-platform Docker image building

Security & Best Practices

• Distroless Container: Minimal attack surface with non-root user
• Container Signing: Build provenance and security scanning
• Security Policy: Vulnerability reporting guidelines
• Code of Conduct: Community guidelines
• Contributing Guide: Comprehensive contribution documentation

🧪 Testing

• Unit Tests: Complete test coverage for all packages
• Mock Servers: HTTP test servers for realistic integration testing
• Error Scenarios: Comprehensive error handling validation
• Robots.txt Testing: Full robots.txt compliance validation

🐳 Container Features

• Multi-stage Build: Optimized Go compilation with minimal runtime image
• Security Hardened: Non-root user, distroless base, minimal dependencies
• Build Optimization: Proper layer caching and build context exclusions

⚡ Performance Benefits

Compared to Python implementations:

• Lower Memory Usage
• Faster Startup/Shutdown
• Better Concurrency
• Single Binary: No runtime dependencies or package management

🔗 Integration

• ToolHive Compatible: Ready for deployment with ToolHive MCP orchestration
• SSE Transport: Better client compatibility than stdio
• Standard Ports: Configurable via environment variables or flags

📝 Documentation

• Comprehensive README: Setup, usage, and API documentation
• API Reference: Complete MCP tool interface documentation
• Development Guide: Local development and contribution instructions
• Security Documentation: Security policies and best practices