Import project configuration: app/vitest.config.js

Import the existing local project snapshot. This commit organizes existing files; it does not represent newly developed functionality.

app/vitest.config.js

@@ -0,0 +1,12 @@
+import { defineConfig } from 'vitest/config';
+import react from '@vitejs/plugin-react';
+
+export default defineConfig({
+  plugins: [react()],
+  test: {
+    environment: 'jsdom',
+    globals: true,
+    setupFiles: ['./src/test/setup.js'],
+    include: ['src/**/*.{test,spec}.{js,jsx}'],
+  },
+});