Automate release drafting

[kwent]

Summary

• add the official Release Drafter v7.7.0 workflow
• update draft releases on pushes to master
• apply configured labels to pull requests
• run all jobs on Blacksmith
• restrict PyPI publication to v* tags

Release flow

1. Merges to master update the next draft GitHub release only.
2. Publishing that release creates its v* tag.
3. The existing publish workflow builds and uploads that tagged package to PyPI.

Validation

• Release Drafter action pinned to commit 34d80673e067bdc0c24568d3af899c216adcfaa9 (v7.7.0)
• all workflow jobs use blacksmith-2vcpu-ubuntu-2404
• ruff check .
• ruff format --check .