fix: 空评论列表 500，并完善撤回审计与角色说明

空切片 JSON 统一为数组；撤回保留正文供站长阅读，成员侧居中提示与重新编辑；头像支持拖放；角色弹窗补全职责说明并汇入封禁。

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

frontend/app/admin/AdminNav.tsx

@@ -22,6 +22,7 @@ import {
   type RoleUserLike,
 } from "@/lib/roles";
 import { realtime, RT_MODERATION_CHANGED } from "@/lib/realtime";
+import { onDocumentVisible } from "@/lib/visibilityReconcile";
 import Avatar from "@/components/Avatar";
 import RoleBadge from "@/components/RoleBadge";
 
@@ -85,14 +86,11 @@ function usePendingCounts(enabled: boolean) {
     };
     load();
     const off = realtime.on(RT_MODERATION_CHANGED, () => load());
-    const onVisible = () => {
-      if (document.visibilityState === "visible") load();
-    };
-    document.addEventListener("visibilitychange", onVisible);
+    const offVisible = onDocumentVisible(load);
     return () => {
       alive = false;
       off();
-      document.removeEventListener("visibilitychange", onVisible);
+      offVisible();
     };
   }, [enabled]);
   return counts.posts + counts.comments;