feat: added Next.js + Express + MongoDB Template

[gunjanghate]

🚀 Add Next.js + Express + MongoDB Template

Overview
This PR adds a Next.js + Express + MongoDB starter template to Celtrix, providing developers with a modern full-stack solution that bridges a Next.js frontend with a dedicated Express backend and MongoDB integration. Available in both TypeScript and JavaScript variants.

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✨ Key Features

Frontend (Next.js 15)

• App Router with latest Next.js features

• TailwindCSS for responsive, modern styling

• Mobile-first design

• ESLint & Prettier configuration

• Sample components: User management interface

• API integration examples

• Custom 404 page

Backend (Express.js)

• Express 5 with modern middleware

• MongoDB/Mongoose integration

• Security with Helmet and CORS

• Request logging with Morgan

• Full CRUD API for user management

• MVC architecture

• Health check endpoints

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📊 API Endpoints

Method	Endpoint	Description	Response
GET	/api/users	Get all users	Array of users
GET	/api/users/:id	Get user by ID	Single user object
POST	/api/users	Create new user	Created user object
PUT	/api/users/:id	Update user	Updated user object
DELETE	/api/users/:id	Delete user	Success message
GET	/api/health	Health check	System status
GET	/	API info	API documentation

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🔧 CLI Integration & Setup

• Added Next.js + Express + MongoDB option to CLI selection menu

• Template manager updated for new stack structure

• Setup commands:

# Create new project
npx celtrix my-next-express-app
Choose Next.js + Express + MongoDB stack
Select TypeScript or JavaScript
Start development
cd my-next-express-app/client && npm run dev

cd my-next-express-app/server && npm run dev

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🎯 Why This Matters

• Separation of concerns: Frontend and backend scalable independently

• Modern stack: Latest Next.js 15 + Express 5

• Production ready: Security, validation, and error handling built-in

• Developer friendly: TypeScript-first with comprehensive documentation

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🧪 Testing

• Verified all package versions install correctly

• Template copying works for TS and JS

• Frontend builds and runs

• Backend starts and connects to MongoDB

• API endpoints function correctly

• 404 page displays properly

• CLI integration works seamlessly

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Impact:
Adds a modern full-stack alternative to MERN with better separation of concerns, flexible backend scaling, Express ecosystem compatibility, and TypeScript-first development experience.

Closes: [Link to related issue]
Demo: Available via npx celtrix → select new stack option

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[JoeCelaster]

@gunjanghate . Can you drop a sample working video or screenshots ?

[gunjanghate]

https://drive.google.com/file/d/1dxO_Unqt3JNGRUvfEUVBVadf6Vrfosxf/view?usp=sharing

[gunjanghate]

@JoeCelaster

https://drive.google.com/file/d/1dxO_Unqt3JNGRUvfEUVBVadf6Vrfosxf/view?usp=sharing