Set up Jest and React Testing Library

[Code-Paragon]

Problem

The dashboard lacks a testing framework, meaning critical math components and UI states cannot be automatically verified against regressions.

Expected behavior

Jest and React Testing Library are installed and configured natively for Next.js using next/jest.js. A test script is added to package.json.

Files to update

• package.json
• jest.config.js (create)
• jest.setup.js (create)

Project relevance

Establishes the foundation for all future frontend unit testing, which is a strict requirement for financial DeFi interfaces.

Acceptance criteria

• Feature works as described
• Tests are added or updated where needed
• Documentation is updated where needed
• Dependencies @testing-library/react and @testing-library/jest-dom are installed
• No TypeScript, lint, test, or build errors