[Enhancement] Adopt a Modern Python Development Toolchain

[lcy-seso]

The project currently lacks standardized tooling for testing, formatting, linting, and static type checking. Adopting a modern Python toolchain will improve code quality, consistency, and contributor experience, while aligning the project with current community best practices.

Proposed Tooling

Area	Tool	Purpose
Testing	pytest	Unit and integration testing
Linting	ruff	Fast linting, import sorting, and bug detection
Formatting	black	Opinionated, consistent code formatting
Type Checking	mypy	Static type checking using Python type hints

Proposed Changes

• Add the above tools as development dependencies
• Introduce or update pyproject.toml with tool configurations
• Organize tests under a standard tests/ directory
• Update documentation with instructions for:
  • Running tests
  • Running linting / formatting
  • Running type checks
• Add CI checks to enforce these tools