Add the standard Apache License 2.0 (Copyright 2026 Arekejoker) covering
the repository's original scripts, workflows, prompts and documentation.
Third-party materials (author sample images, community pose library,
models/LoRAs) stay with their original authors and are excluded via an
explicit carve-out in the README. validate_package.py now requires the
LICENSE file to exist; SKILL.md declares the license in its frontmatter.
