fix: redact inline file data in prompt logs

[atharvasingh7007]

Summary

• redact file.file_data when prompt JSON is logged, alongside the existing image_url.url and input_audio.data handling
• add a direct redact_data() regression covering inline image, audio, and file payloads while preserving external URLs and file_id
• add a CLI regression proving PDF attachments keep their full payload in the outgoing OpenAI request but are redacted in stored prompt_json

Root cause

PDF attachments are encoded as inline {type: file, file: {file_data: data:application/pdf;base64,...}} payloads before they hit redact_data(), but redact_data() only knew how to scrub image_url.url and input_audio.data. That left the full base64 PDF content in responses.prompt_json.

Testing

• python -m pytest tests/test_cli_openai_models.py
• python -m ruff check .
• python -m mypy llm

Closes #1396