add knip dependency to login app

Author: jnsdls

apps/login/package.json

@@ -26,6 +26,7 @@
     "@types/react-dom": "19.0.3",
     "eslint": "^9",
     "eslint-config-next": "15.1.6",
+    "knip": "5.43.6",
     "postcss": "8.5.1",
     "tailwindcss": "3.4.17",
     "typescript": "5.7.3"