feat(admin): 独立后台壳、站点分析与聊天监管，公开站拆出主题切换与访问埋点

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/components/VisitBeacon.tsx

@@ -0,0 +1,23 @@
+"use client";
+
+import { useEffect, useRef } from "react";
+import { usePathname } from "next/navigation";
+import { apiTelemetryPageView } from "@/lib/api";
+
+/**
+ * 公开站页面访问埋点：同 path 30s 内合并；跳过 /admin。
+ */
+export default function VisitBeacon() {
+  const pathname = usePathname();
+  const lastRef = useRef<{ path: string; at: number }>({ path: "", at: 0 });
+
+  useEffect(() => {
+    if (!pathname || pathname === "/admin" || pathname.startsWith("/admin/")) return;
+    const now = Date.now();
+    if (lastRef.current.path === pathname && now - lastRef.current.at < 30_000) return;
+    lastRef.current = { path: pathname, at: now };
+    void apiTelemetryPageView();
+  }, [pathname]);
+
+  return null;
+}