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/content.ts

@@ -17,10 +17,46 @@ export function highlightMentions(text: string, _onClick?: (name: string) => voi
 
 export function formatTime(iso: string) {
   const d = new Date(iso);
+  if (Number.isNaN(d.getTime())) return iso;
+
   const now = new Date();
   const diff = (now.getTime() - d.getTime()) / 1000;
   if (diff < 60) return '刚刚';
   if (diff < 3600) return `${Math.floor(diff / 60)}分钟前`;
   if (diff < 86400) return `${Math.floor(diff / 3600)}小时前`;
-  return `${d.getMonth() + 1}-${d.getDate()} ${String(d.getHours()).padStart(2, '0')}:${String(d.getMinutes()).padStart(2, '0')}`;
+
+  const pad = (n: number) => String(n).padStart(2, '0');
+  const clock = `${pad(d.getHours())}:${pad(d.getMinutes())}`;
+
+  const yesterday = new Date(now);
+  yesterday.setDate(yesterday.getDate() - 1);
+  if (
+    d.getFullYear() === yesterday.getFullYear()
+    && d.getMonth() === yesterday.getMonth()
+    && d.getDate() === yesterday.getDate()
+  ) {
+    return `昨天 ${clock}`;
+  }
+
+  if (d.getFullYear() === now.getFullYear()) {
+    return `${d.getMonth() + 1}月${d.getDate()}日 ${clock}`;
+  }
+
+  return `${d.getFullYear()}年${d.getMonth() + 1}月${d.getDate()}日 ${clock}`;
+}
+
+/** 完整日期时间（用于帖子发布/修改时间展示） */
+export function formatDateTime(iso: string) {
+  const d = new Date(iso);
+  if (Number.isNaN(d.getTime())) return iso;
+  const pad = (n: number) => String(n).padStart(2, '0');
+  return `${d.getFullYear()}年${d.getMonth() + 1}月${d.getDate()}日 ${pad(d.getHours())}:${pad(d.getMinutes())}`;
+}
+
+/** 判断两个 ISO 时间是否相差超过 1 分钟 */
+export function isTimeDiffSignificant(a: string, b: string) {
+  const da = new Date(a).getTime();
+  const db = new Date(b).getTime();
+  if (Number.isNaN(da) || Number.isNaN(db)) return false;
+  return Math.abs(da - db) > 60_000;
 }