fix(deps): update nextjs monorepo to v15

Author: renovate[bot]

package.json

@@ -15,13 +15,13 @@
     "e2e": "playwright test"
   },
   "dependencies": {
-    "@next/mdx": "14.2.23",
+    "@next/mdx": "15.2.1",
     "@vercel/analytics": "^1.3.1",
     "@vercel/speed-insights": "^1.0.12",
     "dayjs": "^1.11.13",
     "lodash": "^4.17.21",
     "motion": "^10.18.0",
-    "next": "14.2.23",
+    "next": "15.2.1",
     "normalize.css": "8.0.1",
     "react": "19.0.0",
     "react-dom": "19.0.0",
@@ -39,7 +39,7 @@
     "classnames": "2.5.1",
     "encoding": "^0.1.13",
     "eslint": "9.21.0",
-    "eslint-config-next": "14.2.23",
+    "eslint-config-next": "15.2.1",
     "eslint-config-prettier": "10.0.1",
     "graphql": "^16.9.0",
     "graphql-request": "^7.1.0",