fix(deps): update dependency next to v15 [security]

Author: renovate[bot]

package.json

@@ -35,7 +35,7 @@
     "github-slugger": "^2.0.0",
     "katex": "^0.16.11",
     "medium-zoom": "^1.1.0",
-    "next": "14.2.15",
+    "next": "15.5.14",
     "next-pwa": "^5.6.0",
     "next-themes": "^0.3.0",
     "nextjs-google-analytics": "^2.3.7",