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/post/[id]/page.tsx

@@ -24,6 +24,7 @@ import {
   type Board,
   type CommentsResponse,
 } from "@/lib/api";
+import BoardIcon, { boardColor } from "@/components/BoardIcon";
 import { postViewerCookieHeader } from "@/lib/cookies";
 import { getMeCached, getPublicSettingsCached } from "@/lib/serverData";
 import CommentSection from "@/components/CommentSection";
@@ -109,7 +110,7 @@ function formatDateTime(dateStr: string) {
    ============================================================ */
 
 function BoardCard({ board }: { board: Board }) {
-  const colorIdx = Math.max(0, board.color_index ?? 0) % 8;
+  const colorIdx = boardColor(board);
   return (
     <section className="j13-module shrink-0" aria-labelledby="board-card-title">
       <p className="j13-module-title mb-3" id="board-card-title">
@@ -117,9 +118,9 @@ function BoardCard({ board }: { board: Board }) {
       </p>
       <Link href={`/?board=${board.id}`} className="flex items-center gap-3 group">
         <span
-          className={`av-${colorIdx} w-11 h-11 rounded-xl flex items-center justify-center text-lg font-extrabold shrink-0`}
+          className={`av-${colorIdx} w-11 h-11 rounded-xl flex items-center justify-center shrink-0`}
         >
-          {board.name.slice(0, 1)}
+          <BoardIcon icon={board.icon} name={board.name} size={20} />
         </span>
         <span
           className="font-semibold text-[14.5px] truncate group-hover:text-[var(--accent)] transition-colors"