test: Add Vitest + React Testing Library setup (Refs #2)

Frontend/package.json

@@ -3,12 +3,14 @@
   "private": true,
   "version": "0.0.0",
   "type": "module",
-  "scripts": {
-    "dev": "vite",
-    "build": "tsc -b && vite build",
-    "lint": "eslint .",
-    "preview": "vite preview"
-  },
+"scripts": {
+  "dev": "vite",
+  "build": "tsc -b && vite build",
+  "lint": "eslint .",
+  "preview": "vite preview",
+  "test": "vitest",
+  "test:run": "vitest run"
+},
   "dependencies": {
     "react": "^19.2.4",
     "react-dom": "^19.2.4",