Add ENV var to use JSON logging

[quiet-node]

Problem

Currently, the JSON-RPC relay always uses pino-pretty for log formatting, which outputs human-readable, colorized logs. While this is excellent for local development and debugging, it creates challenges in production environments:

1. Log aggregation systems (Elasticsearch, Splunk, Datadog, etc.) work best with structured JSON logs
2. Automated log parsing is difficult with pretty-formatted output
3. Container orchestration platforms (Kubernetes, Docker Swarm) typically expect JSON-formatted logs
4. Performance overhead - pino-pretty adds processing time that isn't necessary in production

The relay currently has no way to disable pretty logging in favor of native JSON output.

Proposed Solution

Add a new environment variable PRETTY_LOGS_ENABLED that allows operators to toggle between pretty-printed and JSON-formatted logging.