feat(admin): scaffold Vite+React admin workspace

apps/admin/vitest.config.ts

@@ -0,0 +1,7 @@
+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.ts'] },
+});