Minor improvement: clarify RPC usage note placement in docs

## Overview

While reviewing the documentation, I noticed that RPC configuration guidance is mentioned in multiple places, but it may not always be immediately visible to developers during onboarding.

## Suggestion

Adding small clarification notes or tips in key onboarding guides (such as "build app" or "concepts") can help developers avoid common misconfiguration issues.

## Benefit

This would improve developer experience and reduce confusion related to RPC endpoints and network configuration.