Add dark mode, i18n, messenger/moderation/verify, admin CRUD parity

Web-tier features completing the AtomCMS→Next.js conversion (slice 2):

UI/UX:
- Dark mode: html.dark CSS-var overrides + ThemeSwitcher (localStorage,
  no-flash boot script) wired into the nav.
- i18n (next-intl, cookie-based / no URL routing): en + it catalogs,
  request.ts, provider in root layout, LanguageSwitcher; shell (nav,
  header, footer) fully translated. URLs + access-guard unchanged.
- globals.css: --muted/--border aliases used across admin pages.

User features:
- /messages: offline messages + friend-request accept (server action
  re-reads session, two directional rows, idempotent).
- Email verification: signed-token /verify route + sendVerification wired
  into register (best-effort, never blocks signup).
- Article reactions: toggle UI on news/[slug] + server action.
- Content moderation service (website_wordfilter + optional OpenAI
  moderations, fail-open) wired into article comments + guestbook.

Admin CRUD parity (Filament replacement):
- /admin/shop (+ new/[id]) packages CRUD + read-only orders.
- /admin/transactions read-only PayPal log.
- /admin/permissions, /admin/tags, /admin/ads (+ new/[id]),
  /admin/help-questions (+ new/[id]), /admin/radio/history,
  /admin/users/[id]/edit. All gated by requireStaff + logStaffActivity.

Verified: tsc 0, vitest 48/48, next build 0 (all routes incl. new
admin CRUD + /messages + /verify).

src/app/layout.tsx

@@ -1,4 +1,6 @@
 import type { Metadata } from "next";
+import { NextIntlClientProvider } from "next-intl";
+import { getLocale, getMessages } from "next-intl/server";
 import { Nunito } from "next/font/google";
 import type { ReactNode } from "react";
 import { Navigation } from "@/components/navigation";
@@ -23,22 +25,35 @@ export const metadata: Metadata = {
 
 export default async function RootLayout({ children }: { children: ReactNode }) {
   await enforceSiteAccess();
+  const locale = await getLocale();
+  const messages = await getMessages();
   return (
-    <html lang="en" className={`app ${nunito.variable}`}>
+    <html lang={locale} className={`app ${nunito.variable}`}>
+      <head>
+        {/* Apply the saved theme before first paint to avoid a light→dark flash. */}
+        <script
+          dangerouslySetInnerHTML={{
+            __html:
+              "try{if(localStorage.getItem('theme')==='dark')document.documentElement.classList.add('dark');}catch(e){}",
+          }}
+        />
+      </head>
       <body
         className="flex min-h-screen flex-col site-bg"
         style={{ backgroundColor: "var(--color-background)" }}
       >
-        <ThemeVars />
-        <TopHeader />
-        <SiteHeader />
-        <Navigation />
-        <main className="overflow-hidden site-bg">
-          <div className="mx-auto mt-10 grid max-w-7xl grid-cols-12 gap-x-3 gap-y-8 p-6 md:mt-0">
-            <div className="col-span-12">{children}</div>
-          </div>
-        </main>
-        <SiteFooter />
+        <NextIntlClientProvider locale={locale} messages={messages}>
+          <ThemeVars />
+          <TopHeader />
+          <SiteHeader />
+          <Navigation />
+          <main className="overflow-hidden site-bg">
+            <div className="mx-auto mt-10 grid max-w-7xl grid-cols-12 gap-x-3 gap-y-8 p-6 md:mt-0">
+              <div className="col-span-12">{children}</div>
+            </div>
+          </main>
+          <SiteFooter />
+        </NextIntlClientProvider>
       </body>
     </html>
   );