feat: add mern turborepo stack

[gunjanghate]

##Add MERN (Turborepo) Stack Option
issue : #65

Summary

This PR introduces a new MERN (Turborepo) monorepo template to the CLI stack selection, enabling users to quickly scaffold a full-stack application with shared tooling across client and server.

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What's Included

• New stack option: MERN (Turborepo) added to index.js selection

• Monorepo structure scaffolded at templates/javascript/mern-turbo:

  • package.json with:

    • Workspaces setup (apps/client, apps/server)
    • npm run dev for parallel execution via Turborepo

  • turbo.json (schema issue fixed)

  • apps/client – React + Vite starter

  • apps/server – Express API with /api/health endpoint

  • Template README.md

• 🛠 templateManager updated to copy entire folder structure

• ⚙️ Installer improved to:

  • Run a single npm install at the repo root
  • Display accurate success instructions (npm run dev)

• Main README updated with new stack documentation

• Added smoke test doc: mern-turbo-smoke.md

• Validated file structure and JSON syntax

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🧪 How to Test Locally

npx celtrix my-monorepo
# Select: MERN (Turborepo)

cd my-monorepo
npm install
npm run dev

• Client: http://localhost:5173/
• Server: http://localhost:4000/api/health

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🚀 Potential Follow-Ups

• TypeScript variant (templates/mern-turbo/typescript)
• Tailwind integration (client)
• Shared packages/ folder (ui, eslint-config, etc.)
• Auth-enabled version
• Workspace-level ESLint / Prettier / test scripts
• .env.example and environment validation

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Let me know if you'd like me to proceed with any of the follow-ups—or I can open a separate PR for the TypeScript version next.

[sivakrishnacode]

HI [gunjanghate],

Kindly verify Client folder ,
vite.config and some other stock files are missing in this repo
and prefer TS first

[gunjanghate]

HI @sivakrishnacode Please check now!

[sivakrishnacode]

In TS folder express file is still in js?

[gunjanghate]

Is it happening after installing?

[sivakrishnacode]

ok let me check tomorrow

[gunjanghate]

OK so I fix that issue.
Actually I refer the other templates and I find their typescript version having server.js so I thought that is the structure I have to follow