feat(settings): 站点界面动画总开关与子开关

管理后台可关全站动画，并细调代码折叠、平滑滚动、装饰入场；统一 lib/motion，尊重系统减少动态效果。

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

frontend/components/home/FeedNewTip.tsx

@@ -9,6 +9,7 @@ import {
   type RtFeedChangedData,
 } from "@/lib/realtime";
 import type { FeedSort } from "@/components/home/FeedTabs";
+import { scrollBehavior } from "@/lib/motion";
 
 interface FeedNewTipProps {
   sort: FeedSort;
@@ -52,7 +53,7 @@ export default function FeedNewTip({
   const handleClick = () => {
     setVisible(false);
     router.refresh();
-    window.scrollTo({ top: 0, behavior: "smooth" });
+    window.scrollTo({ top: 0, behavior: scrollBehavior() });
   };
 
   return (