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/visitors/page.tsx

@@ -0,0 +1,111 @@
+"use client";
+
+import { useEffect, useState } from "react";
+import { Users, UserPlus, Repeat, LogIn } from "lucide-react";
+import { AdminStatCard } from "@/components/admin";
+import { AdminChartCard, NamedBarChart, NamedPieChart } from "@/components/admin/charts";
+import { apiStatsVisitors, type VisitVisitors } from "@/lib/api";
+import { RangeSegmented, StatsState, TableEmpty, formatInt } from "../ui";
+
+export default function VisitorsPage() {
+  const [range, setRange] = useState<"7d" | "30d">("7d");
+  const [data, setData] = useState<VisitVisitors | null>(null);
+  const [loading, setLoading] = useState(true);
+  const [error, setError] = useState("");
+
+  useEffect(() => {
+    let alive = true;
+    setLoading(true);
+    apiStatsVisitors(range)
+      .then((d) => {
+        if (alive) {
+          setData(d);
+          setError("");
+        }
+      })
+      .catch(() => alive && setError("加载失败，请稍后重试"))
+      .finally(() => alive && setLoading(false));
+    return () => {
+      alive = false;
+    };
+  }, [range]);
+
+  if (!data) return <StatsState loading={loading} error={error || undefined} />;
+
+  const devices = data.devices.map((d) => ({ label: d.label || "未知", count: d.count }));
+  const oses = data.oses.map((d) => ({ label: d.label || "未知", count: d.count }));
+  const browsers = data.browsers.map((d) => ({ label: d.label || "未知", count: d.count }));
+  const hourly = data.hourly.map((h) => ({ label: `${h.key}时`, count: h.count }));
+  const totalPv = data.logged_in_pv + data.guest_pv;
+  const totalVisitors = data.new_visitors + data.returning;
+
+  return (
+    <div className="flex flex-col gap-4">
+      <div className="flex items-center justify-between gap-2 flex-wrap">
+        <p className="meta text-[12.5px]">基于匿名访客标识（仅存哈希）与登录用户统计。</p>
+        <RangeSegmented value={range} onChange={setRange} />
+      </div>
+
+      {error ? <StatsState error={error} /> : null}
+
+      <div className="grid gap-3 grid-cols-2 xl:grid-cols-4">
+        <AdminStatCard label="登录用户浏览" value={formatInt(data.logged_in_pv)} icon={<LogIn size={17} />} />
+        <AdminStatCard
+          label="游客浏览"
+          value={formatInt(data.guest_pv)}
+          icon={<Users size={17} />}
+          color="var(--ok)"
+          soft="var(--ok-soft, var(--panel-2))"
+        />
+        <AdminStatCard
+          label="新访客"
+          value={formatInt(data.new_visitors)}
+          sub={totalVisitors > 0 ? `${Math.round((data.new_visitors / totalVisitors) * 100)}%` : undefined}
+          hint="统计期内首次出现"
+          icon={<UserPlus size={17} />}
+          color="var(--gold)"
+          soft="var(--gold-soft)"
+        />
+        <AdminStatCard
+          label="回访"
+          value={formatInt(data.returning)}
+          sub={totalVisitors > 0 ? `${Math.round((data.returning / totalVisitors) * 100)}%` : undefined}
+          icon={<Repeat size={17} />}
+          color="var(--ink-2)"
+          soft="var(--panel-2)"
+        />
+      </div>
+
+      {totalPv > 0 ? (
+        <AdminChartCard title="登录 vs 游客" hint={`近 ${data.range_days} 日浏览占比`}>
+          <NamedPieChart
+            data={[
+              { label: "登录用户", count: data.logged_in_pv },
+              { label: "游客", count: data.guest_pv },
+            ]}
+          />
+        </AdminChartCard>
+      ) : null}
+
+      <div className="grid gap-4 lg:grid-cols-3">
+        <AdminChartCard title="设备分布">
+          {devices.length ? <NamedPieChart data={devices} /> : <TableEmpty />}
+        </AdminChartCard>
+        <AdminChartCard title="操作系统 Top 8">
+          {oses.length ? <NamedPieChart data={oses} /> : <TableEmpty />}
+        </AdminChartCard>
+        <AdminChartCard title="浏览器 Top 8">
+          {browsers.length ? <NamedPieChart data={browsers} /> : <TableEmpty />}
+        </AdminChartCard>
+      </div>
+
+      <AdminChartCard title="24 小时活跃分布" hint="各小时浏览量（本地时区）">
+        {hourly.length ? (
+          <NamedBarChart data={hourly} />
+        ) : (
+          <TableEmpty />
+        )}
+      </AdminChartCard>
+    </div>
+  );
+}