docs: improve README with architecture, setup, and structure docs

[Aaradhya-07]

The current setup instructions are a flat bullet list that's easy to miss steps in. This PR restructures the "Setting up Local Development Environment" section into three clear subsections — Requirements, Installation, and Running Locally — each with its own code blocks and links to the relevant tools. All other sections of the README (intro, adding languages, deployment) are preserved unchanged.

[Kunal1522]

hi @Aaradhya-07 thanks for your interest in contributing ..but i think this would make more sense in contributing.md
there is already a pr regarding this #103 although the rest additions are very solid

[robertodauria]

Thanks for the contribution. Closing this as #83 already addresses it. We aim to merge #83 next week, which will give contributors a stable, modern base to work from. We'd encourage you to review it and open any future PRs on top of that.