Introduce two-command local development setup and reproducible sandbox

[Lakshya-2440]

Setting up the project locally currently requires multiple manual steps such as configuring environment variables, installing dependencies, preparing the database, and coordinating services. This often leads to inconsistent environments and onboarding friction for new contributors.

This issue proposes adding a standardized local development workflow that allows contributors to run the project using only:

npm run setup
npm run dev

The setup process should automatically prepare the environment, initialize required services, and verify the application starts successfully. The goal is to make the project reproducible across machines, reduce setup errors, and lower maintainer effort spent on onboarding support.