Make fly-replay logging consistent with regular response logging

Replace inconsistent slog.Info calls with proper AccessLogEntry format
for all fly-replay responses (machine, app, region, and sticky session).
This ensures fly-replay responses now log with the same JSON structure
and fields as regular requests, improving log analysis and monitoring.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: rubys