Add experimental NestJS backend scaffold

[erseco]

Summary

• add a new nest-backend workspace with a minimal NestJS application mirroring the current API entrypoint
• provide starter Users and Projects modules with in-memory storage for early contract tests
• document how to bootstrap the NestJS service and ignore its build artefacts

Testing

• not run

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Codex Task

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Avoid double /v2 prefix when enabling URI versioning

The bootstrap configuration sets app.setGlobalPrefix('api/v2') and also enables URI versioning with default version '2' while every controller is registered for version '2'. In NestJS the version segment is appended after the global prefix, so the effective routes become /api/v2/v2/users and /api/v2/v2/projects. The README states the service should be reachable under http://localhost:3000/api/v2, but those endpoints will 404 because they are mounted under /api/v2/v2/.... Either drop the hard-coded /v2 from the global prefix or disable explicit versioning to expose the endpoints at /api/v2/* as documented.

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