Set up testing framework for the monorepo

[yashdev9274]

Description

Set up a proper testing framework (Jest, Vitest, or Playwright) for the monorepo with appropriate test configurations for each package and app.

Expected Deliverables

• Install testing dependencies in root and/or specific packages
• Create test configuration files (jest.config.js, vitest.config.ts, etc.)
• Add test scripts to package.json
• Create at least one example test file to demonstrate the setup

Areas to Consider

• Unit tests for packages/db (Prisma client)
• Unit tests for packages/auth (authentication logic)
• Component tests for apps/web
• E2E testing for critical user flows