fix(admin): 后台列表切换保留当前内容，去掉加载占位

用户档案、用户列表、内容筛选与公告页等数据到达后再换视图，避免滚动条闪动。

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

frontend/app/admin/content/ContentAdmin.tsx

@@ -1,6 +1,6 @@
 "use client";
 
-import { useCallback, useEffect, useState } from "react";
+import { useCallback, useEffect, useRef, useState } from "react";
 import Link from "next/link";
 import {
   Check,
@@ -153,6 +153,7 @@ export default function ContentAdmin({
   const [appliedQ, setAppliedQ] = useState("");
   const [loading, setLoading] = useState(false);
   const [error, setError] = useState(initError);
+  const loadSeq = useRef(0);
   const [actingKey, setActingKey] = useState<string | null>(null);
 
   const [trustOn, setTrustOn] = useState(initialSettings.trust_reviewed_publish);
@@ -178,34 +179,44 @@ export default function ContentAdmin({
   }, []);
 
   const loadPosts = useCallback(async (page: number, st: AdminContentStatus, q: string) => {
+    const seq = ++loadSeq.current;
     setLoading(true);
     try {
       const res = await apiAdminContentPosts(page, st, q);
+      if (seq !== loadSeq.current) return;
       setPosts(res.posts);
       setPostsTotal(res.total);
       setPostsPage(page);
       setKind("posts");
+      setStatus(st);
+      setAppliedQ(q);
       setError("");
     } catch (e) {
+      if (seq !== loadSeq.current) return;
       setError(e instanceof Error ? e.message : "获取帖子失败");
     } finally {
-      setLoading(false);
+      if (seq === loadSeq.current) setLoading(false);
     }
   }, []);
 
   const loadComments = useCallback(async (page: number, st: AdminContentStatus, q: string) => {
+    const seq = ++loadSeq.current;
     setLoading(true);
     try {
       const res = await apiAdminContentComments(page, st, q);
+      if (seq !== loadSeq.current) return;
       setComments(res.comments);
       setCommentsTotal(res.total);
       setCommentsPage(page);
       setKind("comments");
+      setStatus(st);
+      setAppliedQ(q);
       setError("");
     } catch (e) {
+      if (seq !== loadSeq.current) return;
       setError(e instanceof Error ? e.message : "获取评论失败");
     } finally {
-      setLoading(false);
+      if (seq === loadSeq.current) setLoading(false);
     }
   }, []);
 
@@ -239,7 +250,6 @@ export default function ContentAdmin({
 
   const switchStatus = (st: AdminContentStatus) => {
     if (st === status) return;
-    setStatus(st);
     setError("");
     if (kind === "posts") void loadPosts(1, st, appliedQ);
     else void loadComments(1, st, appliedQ);
@@ -247,13 +257,12 @@ export default function ContentAdmin({
 
   const applySearch = () => {
     const q = keyword.trim();
-    setAppliedQ(q);
     if (kind === "posts") void loadPosts(1, status, q);
     else void loadComments(1, status, q);
   };
 
   const clearSearch = () => {
-    setAppliedQ("");
+    setKeyword("");
     if (kind === "posts") void loadPosts(1, status, "");
     else void loadComments(1, status, "");
   };