feat: Add Node.js dependency installation and environment variable checks

[SynnekOG]

PR Description

Summary

This PR enhances the development tooling workflow by introducing support for Node.js dependencies and automated environment variable validation.

Changes

• Makefile
  • Added node-modules target:
    • Installs Node.js dependencies for tooling (solhint, prettier, prettier-plugin-solidity).
    • Ensures consistent linting and formatting setup across environments.
  • Added env-check target:
    • Verifies required environment variables are set (ALCHEMY_API_KEY, ETHERSCAN_API_KEY, PRIVATE_KEY).
    • Outputs clear ✅/❌ status indicators for each.

Impact

• Simplifies setup for new contributors by automating Node.js dependency installation.
• Prevents misconfiguration by quickly highlighting missing environment variables.
• Improves project reliability and developer experience.

Next Steps

• Extend env-check to include additional required environment variables (e.g., Polygon API keys, Infura).
• Add CI job to run env-check before deployments.
• Consider pinning Node.js dependency versions for deterministic builds.