feat(admin): finalizing modular refactoring with testing suite and UI polish

frontend/vitest.config.ts

@@ -0,0 +1,15 @@
+import { defineConfig } from 'vitest/config';
+import react from '@vitejs/plugin-react';
+import path from 'path';
+
+export default defineConfig({
+  plugins: [react()],
+  test: {
+    environment: 'jsdom',
+    globals: true,
+    setupFiles: ['./vitest.setup.ts'],
+    alias: {
+      '@': path.resolve(__dirname, './'),
+    },
+  },
+});