feat(settings): sidebar layout with profile, security, AI, notifications, nutrition

Sticky sidebar nav. Sections: Profile (name/language), Security (email/password change),
AI & Models (BYOK keys + per-use-case model prefs), Notifications (push subscribe),
Nutrition goals. Sub-pages: API keys, Webhooks.

apps/web/components/settings/settings-page-header.tsx

@@ -0,0 +1,11 @@
+"use client";
+import { useTranslations } from "next-intl";
+export function SettingsPageHeader() {
+  const t = useTranslations("settingsForm");
+  return (
+    <div>
+      <h1 className="text-3xl font-bold tracking-tight">{t("title")}</h1>
+      <p className="text-muted-foreground mt-1">{t("subtitle")}</p>
+    </div>
+  );
+}