升级帖子编辑与 Feed 体验：TipTap 富文本、修订历史、排序与编辑时限。

将 Markdown 编辑器替换为 TipTap WYSIWYG，新增帖子修订记录与 diff 展示；首页支持最新/回复排序与本地缓存；后台可配置编辑时限与锁定帖子；侧边栏整合板块导航并优化 Feed 布局。

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/src/components/FeedSortBar.tsx

@@ -0,0 +1,64 @@
+import { Clock, MessageCircle, Flame } from 'lucide-react';
+import { cn } from '@/lib/utils';
+
+export type FeedSort = 'latest' | 'reply' | 'hot';
+
+const SORT_OPTIONS: {
+  key: FeedSort;
+  label: string;
+  hint: string;
+  icon: typeof Clock;
+}[] = [
+  { key: 'latest', label: '最新发帖', hint: '按发布时间', icon: Clock },
+  { key: 'reply', label: '最新回复', hint: '最近有人回复', icon: MessageCircle },
+  { key: 'hot', label: '热门讨论', hint: '按互动热度', icon: Flame },
+];
+
+interface Props {
+  value: FeedSort;
+  onChange: (sort: FeedSort) => void;
+  postTotal?: number;
+}
+
+export function parseFeedSort(raw: string | null): FeedSort {
+  if (raw === 'reply' || raw === 'hot') return raw;
+  return 'latest';
+}
+
+export function buildHomeUrl(boardId: number, sort: FeedSort = 'latest') {
+  const p = new URLSearchParams();
+  if (boardId) p.set('board', String(boardId));
+  if (sort !== 'latest') p.set('sort', sort);
+  const qs = p.toString();
+  return qs ? `/?${qs}` : '/';
+}
+
+export function feedSortLabel(sort: FeedSort): string {
+  return SORT_OPTIONS.find(o => o.key === sort)?.label ?? '帖子列表';
+}
+
+export default function FeedSortBar({ value, onChange, postTotal }: Props) {
+  return (
+    <div className="feed-toolbar">
+      <div className="feed-sort-bar" role="tablist" aria-label="帖子排序">
+        {SORT_OPTIONS.map(({ key, label, hint, icon: Icon }) => (
+        <button
+          key={key}
+          type="button"
+          role="tab"
+          aria-selected={value === key}
+          title={`${label} · ${hint}`}
+          className={cn('feed-sort-tab', value === key && 'active')}
+          onClick={() => onChange(key)}
+        >
+          <Icon aria-hidden />
+          <span className="feed-sort-tab__label">{label}</span>
+        </button>
+      ))}
+      </div>
+      {postTotal != null && (
+        <span className="feed-toolbar__count">共 {postTotal} 条</span>
+      )}
+    </div>
+  );
+}