feat: add news section with admin editor and public display

- NewsItem type with title, text, date, optional image and link
- Admin page at /admin/news with image upload and auto-date
- Public section between Pricing and FAQ, hidden when empty
- Nav link auto-hides when no news items exist

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/app/admin/layout.tsx

@@ -15,6 +15,7 @@ import {
   Phone,
   FileText,
   Globe,
+  Newspaper,
   LogOut,
   Menu,
   X,
@@ -32,6 +33,7 @@ const NAV_ITEMS = [
   { href: "/admin/schedule", label: "Расписание", icon: Calendar },
   { href: "/admin/pricing", label: "Цены", icon: DollarSign },
   { href: "/admin/faq", label: "FAQ", icon: HelpCircle },
+  { href: "/admin/news", label: "Новости", icon: Newspaper },
   { href: "/admin/contact", label: "Контакты", icon: Phone },
 ];