chore(mobile): update explorer add item icon (#8969)

packages/frontend/core/src/mobile/components/explorer/sections/collections/index.tsx

@@ -6,6 +6,7 @@ import { ExplorerTreeRoot } from '@affine/core/modules/explorer/views/tree';
 import { WorkbenchService } from '@affine/core/modules/workbench';
 import { useI18n } from '@affine/i18n';
 import { track } from '@affine/track';
+import { AddCollectionIcon } from '@blocksuite/icons/rc';
 import { useLiveData, useServices } from '@toeverything/infra';
 import { nanoid } from 'nanoid';
 import { useCallback } from 'react';
@@ -75,6 +76,7 @@ export const ExplorerCollections = () => {
           />
         ))}
         <AddItemPlaceholder
+          icon={<AddCollectionIcon />}
           data-testid="explorer-bar-add-collection-button"
           label={t['com.affine.rootAppSidebar.collection.new']()}
           onClick={() => handleCreateCollection()}

packages/frontend/core/src/mobile/components/explorer/sections/organize/index.tsx

@@ -6,6 +6,7 @@ import {
 import { OrganizeService } from '@affine/core/modules/organize';
 import { useI18n } from '@affine/i18n';
 import track from '@affine/track';
+import { AddOrganizeIcon } from '@blocksuite/icons/rc';
 import { useLiveData, useServices } from '@toeverything/infra';
 import { useCallback, useState } from 'react';
 
@@ -54,6 +55,7 @@ export const ExplorerOrganize = () => {
           <ExplorerFolderNode key={child.id} nodeId={child.id as string} />
         ))}
         <AddItemPlaceholder
+          icon={<AddOrganizeIcon />}
           data-testid="explorer-bar-add-organize-button"
           label={t['com.affine.rootAppSidebar.organize.add-folder']()}
           onClick={() => setOpenNewFolderDialog(true)}

packages/frontend/core/src/mobile/components/explorer/sections/tags/index.tsx

@@ -3,6 +3,7 @@ import { ExplorerTreeRoot } from '@affine/core/modules/explorer/views/tree';
 import { TagService } from '@affine/core/modules/tag';
 import { useI18n } from '@affine/i18n';
 import { track } from '@affine/track';
+import { AddTagIcon } from '@blocksuite/icons/rc';
 import { useLiveData, useServices } from '@toeverything/infra';
 import { useCallback, useState } from 'react';
 
@@ -50,6 +51,7 @@ export const ExplorerTags = () => {
           <ExplorerTagNode key={tag.id} tagId={tag.id} />
         ))}
         <AddItemPlaceholder
+          icon={<AddTagIcon />}
           data-testid="explorer-add-tag-button"
           onClick={() => setShowNewTagDialog(true)}
           label={t[