fix: frontend/package.json to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-POSTCSS-5926692

frontend/package.json

@@ -73,7 +73,7 @@
     "jwt-decode": "^3.1.2",
     "lottie-react": "^2.4.0",
     "markdown-it": "^13.0.1",
-    "next": "^12.3.4",
+    "next": "^13.5.4",
     "nprogress": "^0.2.0",
     "picomatch": "^2.3.1",
     "posthog-js": "^1.58.0",