Improve code quality and update documentation (v2.2.0)

[kekzl]

Code quality improvements:

• Add thread safety with model_lock for concurrent request handling
• Add structured logging module replacing print statements
• Extract configuration constants (SERVER_HOST, SERVER_PORT, etc.)
• Fix bare exception handling with specific exception types
• Add comprehensive input validation in generate_prompt()
• Add unit tests with pytest (tests/test_app.py)

Documentation updates:

• Update README.md with accurate role counts (86 total)
• Add troubleshooting section to README.md
• Add environment variables documentation
• Update CLAUDE.md with v2.2.0 architecture details
• Add testing instructions

Dependencies:

• Add pytest and pytest-cov to dev dependencies
• Add pytest configuration to pyproject.toml
• Bump version to 2.2.0