feat(admin): integrate Next.js admin panel (admin-next/) from feat/nextjs-admin

- Add admin-next/: full Next.js + Prisma + shadcn admin panel (45 API routes, 76 components)
- docker-compose: tg_shop_admin service (port 3000, shared db/shop.db, prisma), bot talks to it via ADMIN_CHAT_URL=http://tg_shop_admin:3000/api/chat
- tor-proxy now proxies onion admin to tg_shop_admin:3000 (new panel)
- chatbotService: ADMIN_CHAT_URL default = http://tg_shop_admin:3000/api/chat (removed localhost:3100 anachronism)
- .env admin secrets gitignored (admin-next/.env)

admin-next/src/lib/chatbot-config.ts

@@ -0,0 +1,38 @@
+// Shared chatbot config cache — used by admin/chatbot and chat routes
+
+let _cachedAt = 0;
+let _cachedConfig: Record<string, string> | null = null;
+const CACHE_TTL = 5 * 60 * 1000; // 5 minutes
+
+export function invalidateChatbotCache() {
+  _cachedAt = 0;
+  _cachedConfig = null;
+}
+
+export function resetCacheTimestamp() {
+  _cachedAt = 0;
+}
+
+export async function getChatbotConfig(): Promise<Record<string, string>> {
+  const now = Date.now();
+  if (_cachedConfig && now - _cachedAt < CACHE_TTL) {
+    return _cachedConfig;
+  }
+
+  // Dynamic import to avoid circular dependency
+  const { db } = await import('@/lib/db');
+  const rows = await db.siteSetting.findMany({
+    where: {
+      key: { startsWith: 'chatbot_' },
+    },
+  });
+
+  const config: Record<string, string> = {};
+  for (const row of rows) {
+    config[row.key] = row.value;
+  }
+
+  _cachedConfig = config;
+  _cachedAt = now;
+  return config;
+}