fix: bump i18next to satisfy react-i18next 17's peer requirement

react-i18next@17 requires i18next >=26.2.0; the root project was still
pinned to ^25.2.1, causing an ERESOLVE conflict on npm ci. Bump
alongside it.

Author: N-thnI

package-lock.json

@@ -25,7 +25,7 @@
     "express": "^4.18.2",
     "express-rate-limit": "^8.6.1",
     "gridstack": "^12.6.0",
-    "i18next": "^25.2.1",
+    "i18next": "^26.3.6",
     "jspdf": "^4.2.1",
     "lucide-react": "^1.27.0",
     "next": "14.2.4",