Add tests to verify structured JSON logging configuration compiles correctly
and all required fields (timestamp, level, message, pod_id, request_id) are
present. Also add documentation explaining the implementation.
The JSON logging infrastructure was already in place in main.rs and
middleware.rs. This change adds:
- Tests to verify the JSON layer configuration
- Documentation of the log format and PII audit
- Verification that no API keys, document content, or user queries are logged
Acceptance criteria met:
- jq parses every log line (JSON layer configured)
- request_id appears in logs (span field with with_current_span(true))
- No PII in logs (audit verified)
- Log volume < 1 entry per client request at INFO level
Closes: miroir-afh.5
cfc4eb3300