fix(deps): update dependency postcss to v8.5.4

Author: renovate[bot]

app/package.json

@@ -82,7 +82,7 @@
     "nats": "^2.17.0",
     "next": "^15.2.1",
     "next-auth": "^4.24.11",
-    "postcss": "8.5.3",
+    "postcss": "8.5.4",
     "react": "^19.0.0",
     "react-chartjs-2": "^5.3.0",
     "react-dom": "^19.0.0",