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/vite.config.ts

@@ -21,7 +21,7 @@ export default defineConfig({
       output: {
         manualChunks(id) {
           if (!id.includes('node_modules')) return;
-          if (id.includes('marked') || id.includes('dompurify')) return 'markdown-vendor';
+          if (id.includes('dompurify')) return 'purify-vendor';
           if (id.includes('@tanstack/react-virtual')) return 'virtual-vendor';
           if (id.includes('@radix-ui') || id.includes('lucide-react')) return 'ui-vendor';
           if (