v0.7.3 — PyPI README rendering fix

Fixed

• PyPI README rendering. The PyPI project page previously showed broken images and broken docs/ / examples/ cross-links because PyPI doesn't resolve relative paths against the source repo. pyproject.toml's readme field now points at a new README-pypi.md — a hand-maintained, slightly-trimmed variant of README.md with every image and cross-link rewritten to absolute https://raw.githubusercontent.com/... or https://github.com/... URLs. The hero banner, diagram1, docs/demo.gif, and every cross-link now render correctly on https://pypi.org/project/aicertify/. The GitHub README.md is unchanged — keep both files in sync when updating Quick Start, comparison table, or examples list.