完善论坛配置与发帖体验：TipTap 富文本、图片上传、修订历史、Feed 排序与后台参数管理。

同步更新 README 与 ROADMAP，反映最新功能与开发状态。

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

frontend/src/hooks/useForumLimits.ts

@@ -0,0 +1,46 @@
+import { useEffect, useState } from 'react';
+import { api } from '../api/client';
+import type { ForumLimitsPublic } from '../api/types';
+
+const DEFAULT_LIMITS: ForumLimitsPublic = {
+  post_title_max: 128,
+  post_tags_max: 256,
+  post_content_max: 50000,
+  comment_max: 5000,
+  search_keyword_min: 1,
+  search_keyword_max: 50,
+  password_min_len: 6,
+  avatar_max_mb: 2,
+};
+
+let cached: ForumLimitsPublic | null = null;
+let inflight: Promise<ForumLimitsPublic> | null = null;
+
+function fetchLimits(): Promise<ForumLimitsPublic> {
+  if (cached) return Promise.resolve(cached);
+  if (inflight) return inflight;
+  inflight = api.forumLimits()
+    .then(limits => {
+      cached = limits;
+      return limits;
+    })
+    .catch(() => DEFAULT_LIMITS)
+    .finally(() => { inflight = null; });
+  return inflight;
+}
+
+/** 获取前台可见的论坛限制配置 */
+export function useForumLimits() {
+  const [limits, setLimits] = useState<ForumLimitsPublic>(cached ?? DEFAULT_LIMITS);
+  const [loading, setLoading] = useState(!cached);
+
+  useEffect(() => {
+    fetchLimits().then(setLimits).finally(() => setLoading(false));
+  }, []);
+
+  return { limits, loading };
+}
+
+export function invalidateForumLimitsCache() {
+  cached = null;
+}