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/app/chat/[id]/ChatRoomClient.tsx

@@ -46,6 +46,7 @@ import type {
 } from "@/lib/realtime";
 import { canOverseeChat } from "@/lib/roles";
 import { toast } from "@/lib/toast";
+import { scrollBehavior } from "@/lib/motion";
 import Avatar from "@/components/Avatar";
 import ConfirmDialog from "@/components/ConfirmDialog";
 import ContextMenu, { type CtxMenuItem } from "@/components/ContextMenu";
@@ -870,7 +871,7 @@ export default function ChatRoomClient({
 
   const scrollToMsg = (id: number) => {
     const el = msgRefs.current.get(id);
-    el?.scrollIntoView({ behavior: "smooth", block: "center" });
+    el?.scrollIntoView({ behavior: scrollBehavior(), block: "center" });
   };
 
   const msgMenuItems = (m: ChatMessage): CtxMenuItem[] => {