refactor: restore Python compatibility and isolate admin transport

[josedab]

Summary

• Restores Python 3.9 support, package metadata, explicit integration gates, and separates private admin HTTP transport.
• Preserves repository public contracts while restoring or strengthening the verification baseline.
• Includes an AUDIT.md where the repository reached the audit/refactor phase.

Commits

• d577c1e fix(python): restore supported runtime baseline
• 5702b5f docs(python): record clean-code audit
• 6173cfc test(python): characterize admin HTTP transport
• 1c6be8b refactor(python): move admin HTTP transport (PY-SRP-1)
• 5d0a61c refactor(python): clarify admin transport policy (PY-SRP-1)
• c01ab68 fix(python): preserve dynamic admin endpoint

Validation

Python 3.9/3.12, 496 tests, Ruff, mypy, package build, and Twine check pass.

Known blockers / deferred work

• None beyond required PR checks and documented AUDIT.md deferrals.

Merge readiness

Ready for review. Merge only after all required GitHub checks and reviewer approvals pass.