Structured logging — stop using console.log in production

Application uses console.log for logging, making it impossible to search, filter, or aggregate logs in production.

Use structured JSON logging: (1) Node: pino (fastest), winston. (2) Python: structlog. (3) Include: timestamp, level, message, request_id, user_id, context. (4) Levels: debug (dev), info (state changes), warn (recoverable), error (failures). (5) Add correlation IDs across services. (6) Ship to aggregator: Datadog, Loki, ELK. (7) Never log sensitive data.

Text logs can't be queried efficiently. JSON logs enable filtering, correlation, and aggregation. At scale, structured logging is essential.