feat(taxonomy): restore descriptive entries for v7.1.0

[PakitoSec]

Summary

• Restore immutable Taxonomy(name, value, verdict) and creation/add/remove APIs; taxonomies are descriptive only and never affect scoring.
• Preserve v6 taxonomy metadata during migration and keep v7.0 text entries readable in Python and the JS SDK.
• Preserve the migration fix for custom v6 relationship types (inert related-to with the original type in the comment).
• Update Python/JS versions and investigation/signal schemas to 7.1.0; regenerate types and demo documents and update renderers/documentation.

Validation

• Python: 596 tests passed, including 27 taxonomy tests.
• JavaScript: 54 tests passed; workspace builds and TypeScript checks passed.
• All pre-commit hooks passed.
• Strict MkDocs build passed.
• Ran scripts/bump_version.py 7.1.0 and scripts/generate.sh.
• Regenerated examples keep the same scores and verdicts.

Release

Release v7.1.0 after required CI checks pass and this PR is merged. The tag-triggered CI publishes to PyPI and npm.