Add comprehensive documentation for lifespan support:
- Add usage examples for both Server and FastMPC classes
- Document startup/shutdown patterns
- Show context access in tools and handlers
- Clean up spacing in test files
This commit integrates FastMCP, a high-level MCP server implementation originally written by Jeremiah Lowin,
into the official MCP SDK. It also updates dependencies and adds new dev dependencies.
It moves the existing SDK into a .lowlevel .