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/i18n/request.ts

@@ -0,0 +1,24 @@
+import { cookies } from "next/headers";
+import { getRequestConfig } from "next-intl/server";
+
+// i18n WITHOUT routing: the locale is chosen by a `NEXT_LOCALE` cookie (set by
+// the language switcher) rather than a URL segment, so every existing route and
+// the access-guard middleware keep working unchanged. English is the fallback.
+export const SUPPORTED_LOCALES = ["en", "it"] as const;
+export type AppLocale = (typeof SUPPORTED_LOCALES)[number];
+export const DEFAULT_LOCALE: AppLocale = "en";
+
+export function isSupportedLocale(value: string | undefined): value is AppLocale {
+  return !!value && (SUPPORTED_LOCALES as readonly string[]).includes(value);
+}
+
+export default getRequestConfig(async () => {
+  const store = await cookies();
+  const cookieLocale = store.get("NEXT_LOCALE")?.value;
+  const locale: AppLocale = isSupportedLocale(cookieLocale) ? cookieLocale : DEFAULT_LOCALE;
+
+  return {
+    locale,
+    messages: (await import(`../messages/${locale}.json`)).default,
+  };
+});