perf(i18n): stop serializing the full catalogue on public pages

The root layout fed the entire ~254 KB message catalogue to
NextIntlClientProvider, which serializes it into the RSC payload of every
page. A public page only reads ~59 KB of it; the ~195 KB difference is staff
tool copy that only /admin, /admin-next and /mod ever render.

The root provider now installs the reduced catalogue and each staff route
group re-installs the full one, since a nested NextIntlClientProvider replaces
the parent message set rather than merging into it. pages.admin.actions stays
public because the shared useServerAction hook runs on public pages too.

Measured: 253 KB -> 59 KB of messages per public page (raw JSON).

Guard tests cover all three halves: the root keeps using the reduced
catalogue, every staff layout installs its own full provider, and no public
tree reads a staff-only namespace.

src/app/admin-next/layout.tsx

@@ -1,4 +1,6 @@
 import { notFound } from "next/navigation";
+import { NextIntlClientProvider } from "next-intl";
+import { getLocale, getMessages } from "next-intl/server";
 import type { ReactNode } from "react";
 import { env } from "@/env";
 import { isHousekeepingPreviewEnabled } from "@/features/housekeeping/foundation/preview-gate";
@@ -27,5 +29,13 @@ export default async function AdminNextLayout({
 		notFound();
 	}
 
-	return children;
+	// Staff tree: re-install the full catalogue the root layout scopes down to
+	// the public subset (nested providers replace the parent set).
+	const [locale, messages] = await Promise.all([getLocale(), getMessages()]);
+
+	return (
+		<NextIntlClientProvider locale={locale} messages={messages}>
+			{children}
+		</NextIntlClientProvider>
+	);
 }

src/app/admin/layout.tsx

@@ -1,7 +1,8 @@
 import { eq } from "drizzle-orm";
 import { LogOut } from "lucide-react";
 import { redirect } from "next/navigation";
-import { getTranslations } from "next-intl/server";
+import { NextIntlClientProvider } from "next-intl";
+import { getLocale, getMessages, getTranslations } from "next-intl/server";
 import type { ReactNode } from "react";
 import { AdminHubChrome } from "@/components/admin/admin-hub-chrome";
 import { AdminMobileWrapper } from "@/components/admin/admin-mobile-wrapper";
@@ -40,8 +41,13 @@ export default async function AdminLayout({
 		if (!u?.twoFactorConfirmedAt) redirect("/settings/2fa?error=staffrequired");
 	}
 
+	// The root layout ships the reduced catalogue so public pages do not carry
+	// the ~195 KB of staff-tool strings. Nested providers replace the parent
+	// set rather than merging, so staff route groups re-install the full one.
+	const [locale, messages] = await Promise.all([getLocale(), getMessages()]);
+
 	return (
-		<>
+		<NextIntlClientProvider locale={locale} messages={messages}>
 			{csrfToken ? <meta name="csrf-token" content={csrfToken} /> : null}
 			<AdminMobileWrapper sidebar={<Sidebar staff={staff} />}>
 				<div
@@ -56,7 +62,7 @@ export default async function AdminLayout({
 				</div>
 			</AdminMobileWrapper>
 			<AdminToaster />
-		</>
+		</NextIntlClientProvider>
 	);
 }
 

src/app/layout.tsx

@@ -13,6 +13,7 @@ import { ThemeVars } from "@/components/theme-vars";
 import { enforceSiteAccess } from "@/lib/access-guard";
 import { getDefaultFaviconDataUri } from "@/lib/default-favicon";
 import { resolveHotelName } from "@/lib/hotel-name";
+import { publicClientMessages } from "@/lib/i18n-client-messages";
 import { siteSettings } from "@/lib/services/site-settings";
 import "./globals.css";
 
@@ -68,7 +69,11 @@ export default async function RootLayout({
 }) {
 	await enforceSiteAccess();
 	const locale = await getLocale();
-	const messages = await getMessages();
+	// Only the namespaces non-staff routes can reach: the full catalogue is
+	// ~254 KB and would otherwise be serialised into every public page's RSC
+	// payload. `/admin`, `/admin-next` and `/mod` install a nested provider
+	// seeded with the full set (see i18n-client-messages).
+	const messages = publicClientMessages(await getMessages());
 	const defaultDark = await siteSettings.getBool("default_dark", false);
 	const nitroUrl = await siteSettings.get("nitro_client_url", "");
 	const nonce = (await headers()).get("x-nonce") ?? undefined;

src/app/mod/layout.tsx

@@ -10,7 +10,8 @@ import {
 	Users,
 } from "lucide-react";
 import { redirect } from "next/navigation";
-import { getTranslations } from "next-intl/server";
+import { NextIntlClientProvider } from "next-intl";
+import { getLocale, getMessages, getTranslations } from "next-intl/server";
 import type { ReactNode } from "react";
 import { LanguageSwitcher } from "@/components/language-switcher";
 import Link from "@/components/link";
@@ -81,8 +82,13 @@ export default async function ModLayout({ children }: { children: ReactNode }) {
 		{ href: "/mod/team", label: t("nav.team"), icon: Users, show: showTeam },
 	].filter((item) => item.show);
 
+	// The root layout ships the reduced catalogue so public pages do not carry
+	// the ~195 KB of staff-tool strings. Nested providers replace the parent
+	// set rather than merging, so staff route groups re-install the full one.
+	const [locale, messages] = await Promise.all([getLocale(), getMessages()]);
+
 	return (
-		<>
+		<NextIntlClientProvider locale={locale} messages={messages}>
 			{csrfToken ? <meta name="csrf-token" content={csrfToken} /> : null}
 			<div
 				data-admin
@@ -140,6 +146,6 @@ export default async function ModLayout({ children }: { children: ReactNode }) {
 				</header>
 				<main className="mx-auto max-w-6xl p-4 sm:p-6">{children}</main>
 			</div>
-		</>
+		</NextIntlClientProvider>
 	);
 }