chore: install v8 coverage for vitest

Author: Eric-Zhang-Developer

package-lock.json

@@ -30,6 +30,7 @@
     "@types/react": "^19",
     "@types/react-dom": "^19",
     "@vitejs/plugin-react": "^5.1.0",
+    "@vitest/coverage-v8": "^4.0.4",
     "eslint": "^9",
     "eslint-config-next": "15.5.3",
     "jsdom": "^27.0.1",