feat: Markdown 工具栏编辑器与服务端预览

共用 md_editor 于发帖/改帖/评论，扩展 ComposeBodyToHTML，并提供 /compose/preview。

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

templates/compose.tmpl

@@ -63,20 +63,21 @@
     <label>标签
       <input name="tags" maxlength="{{.TagsMax}}" value="{{.Tags}}" placeholder="逗号分隔，可选"/>
     </label>
-    <label>正文
-      <textarea name="content" id="compose-content" rows="16" required maxlength="{{.ContentMax}}" placeholder="支持纯文本；图片上传后插入 Markdown 图片语法">{{.Content}}</textarea>
-    </label>
-    <div class="j13-compose__tools">
-      <label class="j13-btn-secondary j13-filebtn">
-        插入图片
-        <input type="file" id="compose-image" accept="image/*" hidden/>
-      </label>
-      <button type="button" class="j13-btn-secondary" id="compose-gate-login" data-gate="login">登录可见</button>
-      <button type="button" class="j13-btn-secondary" id="compose-gate-reply" data-gate="reply">回复可见</button>
-      <button type="button" class="j13-btn-secondary" id="compose-gate-points" data-gate="points">积分可见</button>
-      <span class="j13-muted" id="compose-upload-status"></span>
-    </div>
-    <p class="j13-muted">门控：选中正文后点按钮包裹；积分可见会询问价格（1–9999）。含门控时正文以 HTML 提交。</p>
+    <label>正文</label>
+    {{template "shared/md_editor" (dict
+      "Name" "content"
+      "ID" "compose-content"
+      "Content" .Content
+      "Rows" 16
+      "MaxLength" .ContentMax
+      "Placeholder" "支持 Markdown：标题/粗斜体/列表/代码块/链接；可用工具栏插入图片与门控块"
+      "CSRF" .CSRF
+      "ShowGates" 1
+      "ShowUpload" 1
+      "Unsaved" 1
+      "Required" 1
+    )}}
+    <p class="j13-muted">门控：选中正文后点按钮包裹；积分可见会询问价格（1–9999）。含门控时正文以 HTML 提交。Tab 缩进，可切换预览。</p>
     <button type="submit">{{if .IsEdit}}保存{{else}}发布{{end}}</button>
   </form>
 </main>