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/components/admin/AdminShell.tsx

@@ -24,6 +24,8 @@ import {
   FileText,
   CircleDollarSign,
   Columns3,
+  PanelLeft,
+  BarChart3,
 } from "lucide-react";
 import type { User } from "@/lib/api";
 import { apiAdminPendingCounts, apiLogout } from "@/lib/api";
@@ -64,6 +66,7 @@ const NAV_GROUPS: NavGroup[] = [
     title: "概览",
     items: [
       { href: "/admin", label: "仪表盘", icon: LayoutDashboard, exact: true, visible: () => true },
+      { href: "/admin/analytics", label: "访问统计", icon: BarChart3, visible: (u) => isSuperOrOwner(u.role) },
     ],
   },
   {
@@ -145,6 +148,12 @@ const NAV_GROUPS: NavGroup[] = [
         icon: Palette,
         visible: (u) => isSuperOrOwner(u.role),
       },
+      {
+        href: "/admin/sidebar",
+        label: "侧栏管理",
+        icon: PanelLeft,
+        visible: (u) => isSuperOrOwner(u.role),
+      },
     ],
   },
 ];