Add .nvmrc and .node-version files

[Fatimasanusi]

The project has no pinned Node.js version. Add .nvmrc and .node-version files specifying the required Node.js version (e.g., 20.x). Also add an engines field in both package.json files.
Checklist:

• Add .nvmrc with Node version
• Add .node-version with same version
• Add engines field in frontend/package.json
• Add engines field in backend/package.json

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[Chrisbankz0]

@Chrisbankz0 has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

I would love to work on this issue. I have experience building production ready applications and collaborating through GitHub workflows. I'll carefully analyze the current implementation, propose a reliable solution, and submit a well-tested PR. My focus is on clean code, maintainability, and timely delivery

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Chrisbankz0 to this issue.

[drips-wave]

Congratulations, @Chrisbankz0! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 30, 2026.

🧑‍💻 @Chrisbankz0: Please resolve the issue such that the repo's maintainers have enough time to review your contribution before the due date. You'll earn Points for completing the issue on-time, which will make you eligible for a share of the Stellar Wave Program's reward pool.

Warning

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