refactor(version): centralize Pacta version using package metadata

[PraaneshSelvaraj]

This change centralizes how Pacta’s version is handled by using package metadata as the single source of truth, instead of keeping hard-coded version strings in source files and tests.

The version is now defined only in pyproject.toml and read dynamically at runtime using importlib.metadata. This helps avoid duplication and keeps the CLI output, reporting, and tests in sync automatically.

A default fallback version (0.0.0-dev) is used when package metadata may not be available. Happy to adjust this if you’d prefer a different fallback value.

Fixes: #31

[akhundMurad]

LGTM, but you need to run make format first

[PraaneshSelvaraj]

Thanks, Ran make format and pushed the updated changes.