feat: 管理端板块管理与旧版数据导入，补充部署运营文档

- 新增管理端板块管理页面与后端接口（admin_board）
- 新增旧版数据导入：legacyimport 服务、导入面板、importusers 命令行工具
- 聊天用户卡片、板块图标等 UI 组件与界面优化
- 补充 about/公告/1Panel 部署等文档
- gitignore 排除 dist/ 构建产物与 .agents/ 本地工具目录

frontend/app/admin/pages/PageComposeClient.tsx

@@ -3,7 +3,7 @@
 import { useEffect, useMemo, useRef, useState } from "react";
 import Link from "next/link";
 import { useRouter, useSearchParams } from "next/navigation";
-import { ArrowLeft, Copy, ExternalLink, Loader2 } from "lucide-react";
+import { ArrowLeft, Copy, ExternalLink, FileText, Loader2 } from "lucide-react";
 import {
   apiAdminCreateSitePage,
   apiAdminUpdateSitePage,
@@ -283,34 +283,68 @@ export default function PageComposeClient({
 
   return (
     <div className="admin-doc-page admin-doc-editor">
-      <header className="admin-doc-head">
-        <div className="min-w-0">
-          <Link href={backHref} className="admin-doc-back">
-            <ArrowLeft size={14} aria-hidden /> 返回列表
-          </Link>
-          <div className="admin-doc-head-title">
+      <header className="admin-doc-sticky">
+        <div className="admin-doc-sticky-inner">
+          <div className="admin-doc-sticky-title">
+            <Link href={backHref} className="admin-doc-back" aria-label="返回单页列表">
+              <ArrowLeft size={15} aria-hidden />
+              <span className="admin-doc-back-text">返回列表</span>
+            </Link>
+            <span className="admin-doc-sticky-icon" aria-hidden>
+              <FileText size={15} />
+            </span>
             <h1>{isEdit ? "编辑单页" : "新建单页"}</h1>
             <AdminStatusChip tone={savedPublished ? "ok" : savedPublished === false ? "warn" : "accent"}>
               {savedPublished ? "已发布" : savedPublished === false ? "草稿" : "尚未保存"}
             </AdminStatusChip>
           </div>
+          <div className="admin-doc-sticky-actions">
+            {canViewOnline && savedPage ? (
+              <a
+                href={sitePagePublicPath(savedPage.slug)}
+                target="_blank"
+                rel="noopener noreferrer"
+                className="btn btn-line btn-sm"
+                title="打开已发布内容。未保存的修改不会出现在这里。"
+              >
+                <ExternalLink size={14} aria-hidden /> 线上页面
+              </a>
+            ) : null}
+            <AdminSegmented<PublishKey>
+              role="group"
+              ariaLabel="保存后状态"
+              size="sm"
+              value={form.published ? "published" : "draft"}
+              onChange={(key) => patchForm({ published: key === "published" })}
+              options={[
+                { key: "draft", label: "草稿" },
+                { key: "published", label: "发布" },
+              ]}
+            />
+            <button type="button" className="btn btn-line btn-sm" disabled={!dirty || saving} onClick={discard}>
+              撤销修改
+            </button>
+            <button
+              type="button"
+              className="btn btn-primary btn-sm"
+              disabled={!dirty || saving}
+              onClick={requestSave}
+              aria-busy={saving || undefined}
+            >
+              {saving ? <Loader2 size={14} className="animate-spin" aria-hidden /> : null}
+              {saving ? "保存中…" : saveLabel}
+            </button>
+            <p className={`admin-doc-status${errors.form ? " is-error" : ""}`} aria-live="polite">
+              {statusText}
+            </p>
+          </div>
         </div>
-        {canViewOnline && savedPage ? (
-          <a
-            href={sitePagePublicPath(savedPage.slug)}
-            target="_blank"
-            rel="noopener noreferrer"
-            className="btn btn-line"
-            title="打开已发布内容。未保存的修改不会出现在这里。"
-          >
-            <ExternalLink size={14} aria-hidden /> 查看线上页面
-          </a>
-        ) : null}
       </header>
 
       <div className="admin-doc-split">
         <div className="admin-doc-main">
           <AdminField
+            className="admin-doc-title"
             id="page-title"
             label="标题"
             maxLength={200}
@@ -437,50 +471,8 @@ export default function PageComposeClient({
               />
               <p className="admin-doc-hint">数字越小越靠前，可以为负数。</p>
             </div>
-
-            <div className="admin-doc-field">
-              <p className="admin-doc-label">保存后状态</p>
-              <AdminSegmented<PublishKey>
-                role="group"
-                ariaLabel="保存后状态"
-                size="sm"
-                value={form.published ? "published" : "draft"}
-                onChange={(key) => patchForm({ published: key === "published" })}
-                options={[
-                  { key: "draft", label: "草稿" },
-                  { key: "published", label: "已发布" },
-                ]}
-              />
-              <p className="admin-doc-hint">点选只改变这次要保存的状态，不会立刻发布或下线。</p>
-            </div>
           </div>
         </details>
-
-        <div className="admin-doc-actions" aria-busy={saving || undefined}>
-          <div className="admin-doc-actions-btns">
-            <button type="button" className="btn btn-line" disabled={!dirty || saving} onClick={discard}>
-              撤销修改
-            </button>
-            <button
-              type="button"
-              className="btn btn-primary"
-              disabled={!dirty || saving}
-              onClick={requestSave}
-            >
-              {saving ? <Loader2 size={15} className="animate-spin" aria-hidden /> : null}
-              {saving ? "保存中…" : saveLabel}
-            </button>
-            <p className={`admin-doc-status${errors.form ? " is-error" : ""}`} aria-live="polite">
-              {statusText}
-            </p>
-          </div>
-          <p className="admin-doc-hint">一次保存会写入标题、正文和页面设置。Ctrl/⌘ + Enter 与这个按钮相同。</p>
-          {canViewOnline ? (
-            <p className="admin-doc-hint">查看线上页面打开的是已发布内容，未保存的修改不会出现在那里。</p>
-          ) : (
-            <p className="admin-doc-hint">草稿没有公开地址。要看正文，用编辑器里的预览。</p>
-          )}
-        </div>
       </div>
 
       <ConfirmDialog