fix(deps): update next.js to v15.5.6

Author: renovate[bot]

package.json

@@ -63,7 +63,7 @@
     "fuse.js": "7.1.0",
     "katex": "0.16.22",
     "motion": "12.23.22",
-    "next": "15.5.4",
+    "next": "15.5.6",
     "next-auth": "4.24.11",
     "next-mdx-remote": "5.0.0",
     "next-themes": "0.4.6",
@@ -105,7 +105,7 @@
     "autoprefixer": "10.4.21",
     "dotenv-cli": "10.0.0",
     "eslint": "8.57.0",
-    "eslint-config-next": "15.5.4",
+    "eslint-config-next": "15.5.6",
     "eslint-config-prettier": "9.1.0",
     "eslint-plugin-import": "2.32.0",
     "eslint-plugin-prettier": "5.5.4",