deps: update nextjs monorepo to v16

Author: renovate[bot]

apps/clearance_ui/package.json

@@ -67,7 +67,7 @@
         "zustand": "5.0.10"
     },
     "devDependencies": {
-        "@next/eslint-plugin-next": "15.5.9",
+        "@next/eslint-plugin-next": "16.1.5",
         "@playwright/test": "1.58.0",
         "@tailwindcss/postcss": "^4.0.0",
         "@testing-library/jest-dom": "6.9.1",
@@ -81,7 +81,7 @@
         "eslint-config-custom": "*",
         "jest": "30.2.0",
         "jest-environment-jsdom": "30.2.0",
-        "next": "15.5.9",
+        "next": "16.1.5",
         "next-router-mock": "1.0.5",
         "tailwindcss": "^4.0.0",
         "ts-jest": "29.4.6",