Capture response status code in send_with_header closure via nonlocal.
After awaiting the app, emit a structured log line via
structlog.get_logger("docuvault.access").info("request_complete", ...)
so duration_ms is actually written to the log before contextvars are
cleared by the next request.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>