Summary

• Link docs references for environment variables to the root ENVIRONMENT-VARIABLES.md file
• Add subtle configuration-reference links from Quick Start, Migrate, Running & Deployment, Settings, Features, and OpenTelemetry docs
• Keep the root ENVIRONMENT-VARIABLES.md as the single source of truth, avoiding a duplicate in-app docs page

Validation

• SECRET_KEY=test-secret-key-for-tests-only-32-bytes ./check.sh