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/home/BoardPanels.tsx

@@ -25,7 +25,7 @@ import { formatCompact } from "@/lib/format";
 
 /* ---------- 1. 板块管理员 ---------- */
 
-function Moderators({ items }: { items: BoardModerator[] }) {
+export function Moderators({ items }: { items: BoardModerator[] }) {
   return (
     <section className="j13-module" aria-label="板块管理员">
       <p className="j13-module-title mb-2">
@@ -56,7 +56,7 @@ function Moderators({ items }: { items: BoardModerator[] }) {
 
 /* ---------- 2. 板块概况 ---------- */
 
-function BoardIntro({ board }: { board: BoardWithCount }) {
+export function BoardIntro({ board }: { board: BoardWithCount }) {
   return (
     <section className="j13-module" aria-label="板块概况">
       <p className="j13-module-title mb-2">
@@ -82,7 +82,7 @@ function BoardIntro({ board }: { board: BoardWithCount }) {
 
 /* ---------- 3. 板块数据 + 签到 ---------- */
 
-function BoardPulse({
+export function BoardPulse({
   stats,
   checkin,
   allowComments,
@@ -156,7 +156,7 @@ function BoardPulse({
 
 /* ---------- 4. 本板热门 ---------- */
 
-function BoardHot({ posts, allowComments }: { posts: PostListItem[]; allowComments: boolean }) {
+export function BoardHot({ posts, allowComments }: { posts: PostListItem[]; allowComments: boolean }) {
   return (
     <section className="j13-module" aria-label="本板热门">
       <p className="j13-module-title mb-1.5">
@@ -196,7 +196,7 @@ function BoardHot({ posts, allowComments }: { posts: PostListItem[]; allowCommen
 
 /* ---------- 5. 本板活跃 ---------- */
 
-function BoardActive({ users, allowComments }: { users: ActiveUser[]; allowComments: boolean }) {
+export function BoardActive({ users, allowComments }: { users: ActiveUser[]; allowComments: boolean }) {
   return (
     <section className="j13-module" aria-label="本板活跃成员">
       <p className="j13-module-title mb-2">