chore(backend): clarify nodemon test ignore configuration (#1081)

[Hikmaholadele]

Closes #1081

Summary

This PR updates the backend nodemon configuration to better reflect the project's current layout and clarifies how test files interact with the development server.

Changes

• Updated backend/nodemon.json to remove or correct misleading test ignore patterns.
• Added documentation explaining how nodemon's watch scope relates to the backend/tests directory.
• Improved configuration clarity for contributors without changing runtime behavior.

Why

The previous configuration included ignore patterns for test files under src, while the project's test suite lives under backend/tests. Since nodemon watches only the configured directories, those ignore patterns were misleading and could cause confusion for contributors.

Testing

• Verified backend/nodemon.json is valid.
• Ran the project's relevant validation checks (lint/tests/typecheck as applicable).
• Confirmed the changes do not alter the development server entrypoint or watch behavior beyond clarifying the configuration.

Closes #1081