Design a logging and observability architecture for a platform with 200+ containerized microservices.

Cover: structured (JSON) logging with a consistent correlation/trace ID propagated across service calls for distributed tracing; centralized log aggregation (e.g., a Loki or ELK-style stack) with tiered retention (hot/warm/cold) to manage cost at this scale; Prometheus-style metrics with consistent labeling conventions across services so dashboards/alerts can be templated rather than built per-service; distributed tracing (e.g., OpenTelemetry) to follow a single request across many services; and SLO-based alerting per service feeding a unified on-call/escalation system, with dashboards organiz