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/admin/ads/new/page.tsx

@@ -0,0 +1,19 @@
+import Link from "next/link";
+import { createAd } from "@/actions/admin-ads";
+
+export default function NewAd() {
+  return (
+    <main>
+      <p className="muted">
+        <Link href="/admin/ads">← Advertisements</Link>
+      </p>
+      <h1>New advertisement</h1>
+      <form action={createAd} className="card" style={{ display: "grid", gap: "0.6rem" }}>
+        <input name="image" placeholder="Image URL" required maxLength={255} />
+        <button type="submit" className="btn btn-primary">
+          Create
+        </button>
+      </form>
+    </main>
+  );
+}