Update packaging and documentation for PyPI release 0.3.1

[francescobianco]

This pull request introduces several improvements to the project metadata and documentation, and adds a new test script to verify environment variable handling for server startup. The main highlights are enhanced pyproject.toml metadata for better discoverability, improved documentation formatting and clarity, and a new shell test to ensure the MCP_PORT environment variable works as intended.

Project metadata enhancements:

• Expanded the pyproject.toml file with a more descriptive summary, additional keywords, classifiers, author and maintainer information, and project URLs for easier discovery and package management. [1] [2]

Documentation improvements:

• Improved formatting and organization in docs/readme-pypi.md by adding section breaks for better readability and navigation. [1] [2] [3] [4] [5]

Testing and validation:

• Added a new shell script tests/env/test-mcp-port.sh that verifies the server respects the MCP_PORT environment variable by checking that it binds to the correct port and not the default when overridden.