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/users/UsersAdmin.tsx

@@ -10,7 +10,6 @@ import {
   ExternalLink,
   FolderSearch,
   History,
-  Loader2,
   Monitor,
   ShieldAlert,
   ShieldCheck,
@@ -151,6 +150,9 @@ export default function UsersAdmin({
       setUsers(res.users);
       setSummary(res.summary);
       setTotal(res.total);
+      setFilter(opts.filter);
+      setPage(opts.page);
+      setAppliedQ(opts.q);
       setError("");
     } catch (e) {
       if (seq !== seqRef.current) return;
@@ -166,8 +168,6 @@ export default function UsersAdmin({
     debounceRef.current = setTimeout(() => {
       const q = keyword.trim();
       if (q !== appliedQ) {
-        setAppliedQ(q);
-        setPage(1);
         load({ page: 1, filter, q });
       }
     }, 400);
@@ -195,8 +195,6 @@ export default function UsersAdmin({
   const submitSearch = () => {
     const q = keyword.trim();
     if (q === appliedQ) return;
-    setAppliedQ(q);
-    setPage(1);
     load({ page: 1, filter, q });
   };
 
@@ -204,16 +202,12 @@ export default function UsersAdmin({
   const clearSearch = () => {
     setKeyword("");
     if (appliedQ !== "" || page !== 1) {
-      setAppliedQ("");
-      setPage(1);
       load({ page: 1, filter, q: "" });
     }
   };
 
   const changeFilter = (f: UserFilter) => {
     if (f === filter) return;
-    setFilter(f);
-    setPage(1);
     load({ page: 1, filter: f, q: appliedQ });
   };
 
@@ -221,7 +215,6 @@ export default function UsersAdmin({
     const totalPages = Math.max(1, Math.ceil(total / PAGE_SIZE));
     const next = Math.min(Math.max(1, p), totalPages);
     if (next === page) return;
-    setPage(next);
     load({ page: next, filter, q: appliedQ });
   };
 
@@ -467,13 +460,9 @@ export default function UsersAdmin({
           </div>
         )}
 
-        <div aria-busy={loading} style={{ opacity: loading ? 0.55 : 1, transition: "opacity .15s" }}>
+        <div aria-busy={loading}>
           {error ? (
             <p className="alert-error m-4">{error}</p>
-          ) : loading && users.length === 0 ? (
-            <div className="flex items-center justify-center gap-2 py-16 meta text-[13px]">
-              <Loader2 size={16} className="animate-spin" /> 加载中…
-            </div>
           ) : users.length === 0 ? (
             <AdminEmpty
               icon={<Users size={22} />}
@@ -713,17 +702,15 @@ function LoginLogsDialog({ target, onClose }: { target: AdminUser | null; onClos
       }
     >
       <div className="-mx-1.5 px-1.5 overflow-y-auto flex-1 min-h-0" style={{ maxHeight: "min(52vh, 420px)" }}>
-        {loading ? (
-          <div className="flex items-center justify-center gap-2 py-12 meta text-[13px]">
-            <Loader2 size={16} className="animate-spin" /> 加载中…
-          </div>
-        ) : err ? (
+        {err ? (
           <p className="alert-error my-4">{err}</p>
         ) : logs.length === 0 ? (
-          <div className="text-center py-12">
-            <Monitor size={22} className="mx-auto mb-2" style={{ color: "var(--ink-3)" }} />
-            <p className="meta text-[12.5px]">暂无登录记录</p>
-          </div>
+          loading ? null : (
+            <div className="text-center py-12">
+              <Monitor size={22} className="mx-auto mb-2" style={{ color: "var(--ink-3)" }} />
+              <p className="meta text-[12.5px]">暂无登录记录</p>
+            </div>
+          )
         ) : (
           <ul className="flex flex-col">
             {logs.map((log) => (