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/sidebar/page.tsx

@@ -0,0 +1,46 @@
+import type { Metadata } from "next";
+import { Suspense } from "react";
+import { cookies } from "next/headers";
+import SidebarAdmin from "./SidebarAdmin";
+import { authCookieHeader } from "@/lib/cookies";
+import {
+  fetchAdminSidebar,
+  type SidebarConfig,
+  type SidebarWidgetRecord,
+} from "@/lib/api";
+import { getMeCached } from "@/lib/serverData";
+import { isSuperOrOwner } from "@/lib/roles";
+import Forbidden from "../Forbidden";
+
+export const metadata: Metadata = {
+  title: "侧栏管理",
+};
+
+export default async function AdminSidebarPage() {
+  const cookie = authCookieHeader(await cookies());
+  const me = await getMeCached(cookie || undefined);
+  if (!me.user || !isSuperOrOwner(me.user.role)) {
+    return <Forbidden text="侧栏管理仅超级管理员及以上角色可操作。" />;
+  }
+
+  let config: SidebarConfig | null = null;
+  let widgets: SidebarWidgetRecord[] = [];
+  let initError = "";
+  try {
+    const res = await fetchAdminSidebar(cookie || undefined);
+    config = res.config;
+    widgets = res.widgets ?? [];
+  } catch (e) {
+    initError = e instanceof Error ? e.message : "加载失败";
+  }
+
+  return (
+    <Suspense fallback={<p className="meta px-1 py-6">加载中…</p>}>
+      <SidebarAdmin
+        initialConfig={config}
+        initialWidgets={widgets}
+        initError={initError}
+      />
+    </Suspense>
+  );
+}