feat: scaffold frontend (Vite + React + Vitest)

- Añade scaffold de frontend con Vite y React
- Configura Vitest y tests básicos (App, Navbar)
- Añade QueryClient y hooks/plantillas iniciales

frontend/vite.config.ts

@@ -0,0 +1,28 @@
+import { defineConfig } from 'vite';
+import react from '@vitejs/plugin-react';
+
+export default defineConfig({
+  plugins: [react()],
+  server: {
+    port: 5173,
+  },
+});
+import { defineConfig } from 'vite';
+import react from '@vitejs/plugin-react';
+
+export default defineConfig({
+  plugins: [react()],
+  test: {
+    environment: 'jsdom',
+    globals: true,
+    setupFiles: ['./src/setupTests.ts'],
+    include: ['tests/**/*.spec.tsx'],
+  },
+});
+import { defineConfig } from 'vite';
+import react from '@vitejs/plugin-react';
+
+export default defineConfig({
+  plugins: [react()],
+  server: { port: 5173 },
+});