[Observability] Logging, metrics, and tracing

[OneByJorah]

Observability Checklist

• Structured logging with JSON format (structlog or python-json-logger)
• Add log levels configuration (DEBUG, INFO, WARNING, ERROR)
• Add Prometheus metrics exposition (/metrics endpoint)
• Add key metrics: agent count, SNMP devices, command latency, error rates
• Add OpenTelemetry tracing for distributed tracing
• Add health check endpoints with detailed status
• Add log rotation and retention policies
• Add alerting rules for critical metrics
• Add Grafana dashboard templates