fix(frontend): 聊天页单屏布局并消除 F5 滚底闪烁

锁定视口避免双滚动；消息列表改用 flex-col-reverse，SSR/无 JS 默认贴最新消息。

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

frontend/app/chat/[id]/page.tsx

@@ -66,29 +66,27 @@ export default async function ChatRoomPage({ params }: PageProps) {
       : room.name;
 
   return (
-    <div className="max-w-6xl mx-auto">
-      <ChatShell meId={me.user.id} initialRooms={rooms} activeRoomId={room.id}>
-        <ChatRoomClient
-          roomId={room.id}
-          roomName={displayName}
-          roomDescription={room.description}
-          ownerId={room.owner_id}
-          memberCount={room.member_count}
-          myRole={room.my_role}
-          joined={room.joined}
-          isPrivate={room.is_private}
-          isDefault={room.is_default}
-          roomType={room.room_type || "group"}
-          peer={room.peer || null}
-          meId={me.user.id}
-          meRole={me.user.role}
-          meName={me.user.nickname || me.user.username}
-          meAvatar={me.user.avatar || ""}
-          initialMessages={initialMessages.messages}
-          initialHasMore={initialMessages.has_more}
-          embedded
-        />
-      </ChatShell>
-    </div>
+    <ChatShell meId={me.user.id} initialRooms={rooms} activeRoomId={room.id}>
+      <ChatRoomClient
+        roomId={room.id}
+        roomName={displayName}
+        roomDescription={room.description}
+        ownerId={room.owner_id}
+        memberCount={room.member_count}
+        myRole={room.my_role}
+        joined={room.joined}
+        isPrivate={room.is_private}
+        isDefault={room.is_default}
+        roomType={room.room_type || "group"}
+        peer={room.peer || null}
+        meId={me.user.id}
+        meRole={me.user.role}
+        meName={me.user.nickname || me.user.username}
+        meAvatar={me.user.avatar || ""}
+        initialMessages={initialMessages.messages}
+        initialHasMore={initialMessages.has_more}
+        embedded
+      />
+    </ChatShell>
   );
 }