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/utils/revisionDiff.ts

@@ -0,0 +1,77 @@
+import { diffLines, diffWords } from 'diff';
+import DOMPurify from 'dompurify';
+import { POST_CONTENT_PURIFY_CONFIG } from './postContent';
+
+export interface PostSnapshot {
+  title: string;
+  content: string;
+  tags: string;
+}
+
+export interface RevisionChangeSummary {
+  titleChanged: boolean;
+  tagsChanged: boolean;
+  contentChanged: boolean;
+  hasChanges: boolean;
+}
+
+export interface DiffPart {
+  value: string;
+  added?: boolean;
+  removed?: boolean;
+}
+
+/** 将 HTML 正文转为适合 diff 的纯文本（保留段落换行） */
+export function htmlToDiffText(html: string): string {
+  if (!html.trim()) return '';
+  const doc = new DOMParser().parseFromString(
+    DOMPurify.sanitize(html, POST_CONTENT_PURIFY_CONFIG),
+    'text/html',
+  );
+  doc.querySelectorAll('br').forEach(br => br.replaceWith('\n'));
+  const blocks = doc.querySelectorAll('p, div, li, h1, h2, h3, h4, h5, h6, blockquote, pre, members-only');
+  blocks.forEach(el => {
+    el.prepend(doc.createTextNode('\n'));
+    el.append(doc.createTextNode('\n'));
+  });
+  return (doc.body.textContent ?? '')
+    .replace(/\r\n/g, '\n')
+    .replace(/\n{3,}/g, '\n\n')
+    .trim();
+}
+
+export function summarizeChange(before: PostSnapshot, after: PostSnapshot): RevisionChangeSummary {
+  const titleChanged = before.title.trim() !== after.title.trim();
+  const tagsChanged = normalizeTags(before.tags) !== normalizeTags(after.tags);
+  const contentChanged = htmlToDiffText(before.content) !== htmlToDiffText(after.content);
+  return {
+    titleChanged,
+    tagsChanged,
+    contentChanged,
+    hasChanges: titleChanged || tagsChanged || contentChanged,
+  };
+}
+
+function normalizeTags(tags: string) {
+  return tags.split(/[,，]/).map(t => t.trim()).filter(Boolean).join(',');
+}
+
+export function diffTextLines(before: string, after: string): DiffPart[] {
+  return diffLines(before || '', after || '');
+}
+
+export function diffTextWords(before: string, after: string): DiffPart[] {
+  return diffWords(before || '', after || '');
+}
+
+/** 统计 diff 片段中的增删行数 */
+export function countLineChanges(parts: DiffPart[]) {
+  let added = 0;
+  let removed = 0;
+  for (const p of parts) {
+    const lines = p.value.split('\n').filter(l => l.length > 0);
+    if (p.added) added += lines.length;
+    else if (p.removed) removed += lines.length;
+  }
+  return { added, removed };
+}