Add log sanitization for user data

[NP-compete]

Summary

Add log sanitization to prevent sensitive user data from appearing in logs.

Requirements

• Sanitize user input before logging
• Redact PII (emails, names, etc.)
• Redact tokens and credentials
• Configurable sanitization patterns

Acceptance Criteria

• log_sanitizer.py utility module
• Sanitization applied to request/response logging
• PII patterns detected and redacted
• Tokens/credentials never logged
• Sanitization configurable via settings

[TensorDevLJ]

Hi — I've opened PR #92 that addresses this issue:

#92

Implemented:

• log_sanitizer.py utility for redacting PII, tokens, and sensitive headers
• Sanitization applied in request/response middleware (api.py)
• Removed raw user message logging in stream.py and history.py
• Configurable via LOG_SANITIZATION_ENABLED, LOG_SANITIZE_PII, LOG_SANITIZE_TOKENS
• Added unit tests (88 tests pass locally)

Happy to address any review feedback. Thanks!