Add Testing Setup for Frontend and Backend

Description:

Currently, there are no tests in the project. We need to add a proper testing setup for both the frontend (/gallery) and backend (/api) apps to ensure code reliability, prevent regressions, and make future development safer. After setup, running npm run test in either folder should execute the respective test suites successfully.

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Plan

Frontend (/gallery)

• Use Vitest + React Testing Library for component and UI testing.
• Configure a setupTests.js file.
• Add a sample test for one component (e.g., Hero).
• Add a test script (npm run test) to package.json.

Backend (/api)

• Use Jest + Supertest for API and controller testing.
• Add a simple test for one route (e.g., /api/users).
• Add a test script (npm run test) to package.json.

Optional (Full Stack)

• Integrate Playwright for end-to-end (E2E) tests that check frontend + backend flows.

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Acceptance Criteria

• Frontend test setup using Vitest + RTL is configured.
• Backend test setup using Jest + Supertest is configured.
• Running npm run test in each app executes tests successfully.
• Sample tests pass in both apps.
• Test scripts are added to package.json and also on root package.json.
• (Optional) Playwright setup is ready for future E2E testing.