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/components/language-switcher.tsx

@@ -0,0 +1,45 @@
+"use client";
+
+import { useLocale } from "next-intl";
+import { useRouter } from "next/navigation";
+import { useTransition } from "react";
+
+const LOCALES: { code: string; label: string }[] = [
+  { code: "en", label: "EN" },
+  { code: "it", label: "IT" },
+];
+
+/**
+ * Locale picker. Writes the chosen locale to the `NEXT_LOCALE` cookie (read by
+ * src/i18n/request.ts on the server) and refreshes the route so server
+ * components re-render with the new messages. No URL change — matches the
+ * cookie-based, routing-free i18n setup.
+ */
+export function LanguageSwitcher() {
+  const locale = useLocale();
+  const router = useRouter();
+  const [pending, startTransition] = useTransition();
+
+  function onChange(e: React.ChangeEvent<HTMLSelectElement>) {
+    const next = e.target.value;
+    document.cookie = `NEXT_LOCALE=${next};path=/;max-age=31536000;samesite=lax`;
+    startTransition(() => router.refresh());
+  }
+
+  return (
+    <select
+      value={locale}
+      onChange={onChange}
+      disabled={pending}
+      aria-label="Language"
+      className="nav-item cursor-pointer bg-transparent text-[13px]"
+      style={{ border: "none", padding: "0 0.25rem" }}
+    >
+      {LOCALES.map((l) => (
+        <option key={l.code} value={l.code}>
+          {l.label}
+        </option>
+      ))}
+    </select>
+  );
+}