feat: add vitest for testing and implement tests for calculateDay utility

- Added "test" script to package.json for running vitest.
- Updated api.js to use localhost for backend during development.
- Created utils.spec.js to test calculateDay function with various scenarios.
- Updated vite.config.js to include vitest configuration and conditionally load Vue DevTools.

frontend/src/api/api.js

@@ -4,7 +4,8 @@ import router from '@/router'
 import { useAuthStore } from '@/stores/authStore'
 
 const api = axios.create({
-  baseURL: '/odoo/api', // Twój backend
+  // baseURL: '/odoo/api', // Twój backend
+  baseURL: 'http://localhost:8000', // Twój backend
 })
 
 // Request interceptor – dodawanie tokena