fix: use project's useI18n hook instead of next-intl useTranslations

The project uses a custom i18n provider, not next-intl directly.
This was causing a client-side crash on page load.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/src/components/ui/cookie-consent.tsx

@@ -1,14 +1,14 @@
 "use client";
 
 import { useState, useEffect } from "react";
-import { useTranslations } from "next-intl";
+import { useI18n } from "@/lib/i18n";
 import { motion, AnimatePresence } from "framer-motion";
 import { Button } from "@/components/ui/button";
 
 const STORAGE_KEY = "cookie-consent";
 
 export function CookieConsent() {
-  const t = useTranslations("cookieConsent");
+  const { t } = useI18n();
   const [visible, setVisible] = useState(false);
 
   useEffect(() => {
@@ -42,17 +42,17 @@ export function CookieConsent() {
               </span>
               <div className="flex-1 min-w-0">
                 <h3 className="font-semibold text-foreground mb-1">
-                  {t("title")}
+                  {t("cookieConsent.title")}
                 </h3>
                 <p className="text-sm text-muted-foreground leading-relaxed">
-                  {t("description")}
+                  {t("cookieConsent.description")}
                 </p>
                 <div className="flex flex-wrap items-center gap-3 mt-4">
                   <Button variant="outline" size="sm" onClick={essentialOnly}>
-                    {t("essentialOnly")}
+                    {t("cookieConsent.essentialOnly")}
                   </Button>
                   <Button size="sm" onClick={acceptAll}>
-                    {t("acceptAll")}
+                    {t("cookieConsent.acceptAll")}
                   </Button>
                 </div>
               </div>