Follow-up to Dusk1e's PR #7120 (Slack send_image redirect guard):
- Rename _safe_url_for_log -> safe_url_for_log (drop underscore) since
it is now imported cross-module by the Slack adapter
- Add _ssrf_redirect_guard httpx event hook to cache_image_from_url()
and cache_audio_from_url() in base.py — same pattern as vision_tools
and the Slack adapter fix
- Update url_safety.py docstring to reflect broader coverage
- Add regression tests for image/audio redirect blocking + safe passthrough