add back btn for mobile view (#1861)

src/app/pages/client/space/Search.tsx

@@ -1,5 +1,5 @@
 import React, { useRef } from 'react';
-import { Box, Icon, Icons, Text, Scroll } from 'folds';
+import { Box, Icon, Icons, Text, Scroll, IconButton } from 'folds';
 import { useAtomValue } from 'jotai';
 import { Page, PageContent, PageContentCenter, PageHeader } from '../../../components/page';
 import { MessageSearch } from '../../../features/message-search';
@@ -9,11 +9,14 @@ import { allRoomsAtom } from '../../../state/room-list/roomList';
 import { mDirectAtom } from '../../../state/mDirectList';
 import { roomToParentsAtom } from '../../../state/room/roomToParents';
 import { useMatrixClient } from '../../../hooks/useMatrixClient';
+import { ScreenSize, useScreenSizeContext } from '../../../hooks/useScreenSize';
+import { BackRouteHandler } from '../../../components/BackRouteHandler';
 
 export function SpaceSearch() {
   const mx = useMatrixClient();
   const scrollRef = useRef<HTMLDivElement>(null);
   const space = useSpace();
+  const screenSize = useScreenSizeContext();
 
   const mDirects = useAtomValue(mDirectAtom);
   const roomToParents = useAtomValue(roomToParentsAtom);
@@ -25,12 +28,26 @@ export function SpaceSearch() {
 
   return (
     <Page>
-      <PageHeader>
-        <Box grow="Yes" justifyContent="Center" alignItems="Center" gap="200">
-          <Icon size="400" src={Icons.Search} />
-          <Text size="H3" truncate>
-            Message Search
-          </Text>
+      <PageHeader balance>
+        <Box grow="Yes" alignItems="Center" gap="200">
+          <Box grow="Yes" basis="No">
+            {screenSize === ScreenSize.Mobile && (
+              <BackRouteHandler>
+                {(onBack) => (
+                  <IconButton onClick={onBack}>
+                    <Icon src={Icons.ArrowLeft} />
+                  </IconButton>
+                )}
+              </BackRouteHandler>
+            )}
+          </Box>
+          <Box justifyContent="Center" alignItems="Center" gap="200">
+            {screenSize !== ScreenSize.Mobile && <Icon size="400" src={Icons.Search} />}
+            <Text size="H3" truncate>
+              Message Search
+            </Text>
+          </Box>
+          <Box grow="Yes" basis="No" />
         </Box>
       </PageHeader>
       <Box style={{ position: 'relative' }} grow="Yes">