feat: admin panel with SQLite, auth, and calendar-style schedule editor

Complete admin panel for content management:
- SQLite database with better-sqlite3, seed script from content.ts
- Simple password auth with HMAC-signed cookies (Edge + Node compatible)
- 9 section editors: meta, hero, about, team, classes, schedule, pricing, FAQ, contact
- Team CRUD with image upload and drag reorder
- Schedule editor with Google Calendar-style visual timeline (colored blocks, overlap detection, click-to-add)
- All public components refactored to accept data props from DB (with fallback to static content)
- Middleware protecting /admin/* and /api/admin/* routes

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

src/app/admin/page.tsx

@@ -0,0 +1,58 @@
+import Link from "next/link";
+import {
+  Globe,
+  Sparkles,
+  FileText,
+  Users,
+  BookOpen,
+  Calendar,
+  DollarSign,
+  HelpCircle,
+  Phone,
+} from "lucide-react";
+
+const CARDS = [
+  { href: "/admin/meta", label: "SEO / Мета", icon: Globe, desc: "Заголовок и описание сайта" },
+  { href: "/admin/hero", label: "Главный экран", icon: Sparkles, desc: "Заголовок, подзаголовок, кнопка" },
+  { href: "/admin/about", label: "О студии", icon: FileText, desc: "Текст о студии" },
+  { href: "/admin/team", label: "Команда", icon: Users, desc: "Тренеры и инструкторы" },
+  { href: "/admin/classes", label: "Направления", icon: BookOpen, desc: "Типы занятий" },
+  { href: "/admin/schedule", label: "Расписание", icon: Calendar, desc: "Расписание занятий" },
+  { href: "/admin/pricing", label: "Цены", icon: DollarSign, desc: "Абонементы и аренда" },
+  { href: "/admin/faq", label: "FAQ", icon: HelpCircle, desc: "Часто задаваемые вопросы" },
+  { href: "/admin/contact", label: "Контакты", icon: Phone, desc: "Адреса, телефон, карта" },
+];
+
+export default function AdminDashboard() {
+  return (
+    <div>
+      <h1 className="text-2xl font-bold">Панель управления</h1>
+      <p className="mt-1 text-neutral-400">Выберите раздел для редактирования</p>
+
+      <div className="mt-8 grid gap-4 sm:grid-cols-2 lg:grid-cols-3">
+        {CARDS.map((card) => {
+          const Icon = card.icon;
+          return (
+            <Link
+              key={card.href}
+              href={card.href}
+              className="group rounded-xl border border-white/10 bg-neutral-900 p-5 transition-all hover:border-gold/30 hover:bg-neutral-900/80"
+            >
+              <div className="flex items-center gap-3">
+                <div className="flex h-10 w-10 items-center justify-center rounded-lg bg-gold/10 text-gold">
+                  <Icon size={20} />
+                </div>
+                <div>
+                  <h2 className="font-medium text-white group-hover:text-gold transition-colors">
+                    {card.label}
+                  </h2>
+                  <p className="text-xs text-neutral-500">{card.desc}</p>
+                </div>
+              </div>
+            </Link>
+          );
+        })}
+      </div>
+    </div>
+  );
+}