test: setup vitest for unit testing

test(frontend): add unit tests for api and utils The frontend codebase currently lacks unit test coverage for its core logic layers. This issue aims to add unit tests for:

• API/service layer logic
• Utility/helper functions This merge request adds unit test coverage for the frontend core logic, focusing on both utility helpers and the API/service layer. The goal is to improve reliability, error handling, and maintainability of the frontend codebase. ✅ Utility Tests

Added unit tests for shared utility helpers:

cn (class name merge helper)

decodeJwt

isTokenExpired

Covered:

valid cases

edge cases

invalid input handling

✅ API / Service Layer Tests

Added unit tests for API helper functions using Vitest

Axios calls are mocked to avoid real network requests

Covered:

successful API responses

error handling scenarios

helper functions such as isApiError

Ensured API functions return correctly mapped response data