chore: add vitest testing infrastructure

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

package.json

@@ -15,7 +15,9 @@
     "db:generate": "prisma generate",
     "db:pull": "prisma db pull",
     "db:push": "prisma db push",
-    "db:studio": "prisma studio"
+    "db:studio": "prisma studio",
+    "test": "vitest run",
+    "test:watch": "vitest"
   },
   "keywords": [],
   "author": "",
@@ -53,10 +55,13 @@
     "@types/nodemailer": "^7.0.11",
     "@types/react": "^19.2.14",
     "@types/react-dom": "^19.2.3",
+    "@types/supertest": "^7.2.0",
     "@vitejs/plugin-react": "^6.0.1",
     "concurrently": "^9.2.1",
+    "supertest": "^7.2.2",
     "tsx": "^4.21.0",
     "typescript": "^5.9.3",
-    "vite": "^8.0.0"
+    "vite": "^8.0.0",
+    "vitest": "^4.1.0"
   }
 }