feat: 站点访问统计与可配置侧边栏组件

- 新增访问统计：visitstats 服务与查询、visit_capture 中间件、爬虫/来源识别、管理端 analytics 页面
- 新增侧边栏：sidebar 服务与 handler、管理端 sidebar 配置页、前端侧边栏组件
- 新增 widget 嵌入代码生成（widgetCode）与 widgetApi
- 遥测逻辑迁移至 handler 层，删除 service/telemetry
- env 示例补充 Docker 部署可信代理 IP 说明

frontend/app/admin/analytics/AnalyticsShell.tsx

@@ -0,0 +1,74 @@
+"use client";
+
+import Link from "next/link";
+import { usePathname, useRouter } from "next/navigation";
+import { useRef, type KeyboardEvent, type ReactNode } from "react";
+import { BarChart3 } from "lucide-react";
+import { AdminPageHeader } from "@/components/admin";
+
+export const ANALYTICS_TABS: { href: string; label: string }[] = [
+  { href: "/admin/analytics", label: "概览" },
+  { href: "/admin/analytics/realtime", label: "实时" },
+  { href: "/admin/analytics/sources", label: "来源分析" },
+  { href: "/admin/analytics/pages", label: "受访页面" },
+  { href: "/admin/analytics/visitors", label: "访客画像" },
+  { href: "/admin/analytics/security", label: "爬虫与安全" },
+  { href: "/admin/analytics/details", label: "访问明细" },
+  { href: "/admin/analytics/settings", label: "设置" },
+];
+
+export default function AnalyticsShell({ children }: { children: ReactNode }) {
+  const pathname = usePathname();
+  const router = useRouter();
+  const navRefs = useRef<(HTMLAnchorElement | null)[]>([]);
+
+  // ←→/Home/End 键盘导航，范式同 SettingsShell（纵向改横向）
+  const onNavKeyDown = (e: KeyboardEvent<HTMLAnchorElement>, i: number) => {
+    if (
+      e.key !== "ArrowRight" &&
+      e.key !== "ArrowLeft" &&
+      e.key !== "Home" &&
+      e.key !== "End"
+    ) {
+      return;
+    }
+    e.preventDefault();
+    let next = i;
+    if (e.key === "ArrowRight") next = (i + 1) % ANALYTICS_TABS.length;
+    else if (e.key === "ArrowLeft") next = (i + ANALYTICS_TABS.length - 1) % ANALYTICS_TABS.length;
+    else if (e.key === "Home") next = 0;
+    else next = ANALYTICS_TABS.length - 1;
+    navRefs.current[next]?.focus();
+    router.push(ANALYTICS_TABS[next].href);
+  };
+
+  return (
+    <div className="admin-analytics-page">
+      <AdminPageHeader
+        icon={BarChart3}
+        title="访问统计"
+        description="站点流量、来源、访客与安全事件的采集与分析"
+      />
+      <nav className="admin-analytics-tabs" aria-label="访问统计分类">
+        {ANALYTICS_TABS.map((item, i) => {
+          const active = pathname === item.href;
+          return (
+            <Link
+              key={item.href}
+              ref={(el) => {
+                navRefs.current[i] = el;
+              }}
+              href={item.href}
+              className="admin-analytics-tab"
+              aria-current={active ? "page" : undefined}
+              onKeyDown={(e) => onNavKeyDown(e, i)}
+            >
+              {item.label}
+            </Link>
+          );
+        })}
+      </nav>
+      {children}
+    </div>
+  );
+}