feat(ui): add useBoardTotal hook to get total items in board

actually not using it now, but it's there

invokeai/frontend/web/src/services/api/hooks/useBoardTotal.ts

@@ -0,0 +1,53 @@
+import { skipToken } from '@reduxjs/toolkit/dist/query';
+import {
+  ASSETS_CATEGORIES,
+  BoardId,
+  IMAGE_CATEGORIES,
+  INITIAL_IMAGE_LIMIT,
+} from 'features/gallery/store/gallerySlice';
+import { useMemo } from 'react';
+import { ListImagesArgs, useListImagesQuery } from '../endpoints/images';
+
+const baseQueryArg: ListImagesArgs = {
+  offset: 0,
+  limit: INITIAL_IMAGE_LIMIT,
+  is_intermediate: false,
+};
+
+const imagesQueryArg: ListImagesArgs = {
+  categories: IMAGE_CATEGORIES,
+  ...baseQueryArg,
+};
+
+const assetsQueryArg: ListImagesArgs = {
+  categories: ASSETS_CATEGORIES,
+  ...baseQueryArg,
+};
+
+const noBoardQueryArg: ListImagesArgs = {
+  board_id: 'none',
+  ...baseQueryArg,
+};
+
+export const useBoardTotal = (board_id: BoardId | null | undefined) => {
+  const queryArg = useMemo(() => {
+    if (!board_id) {
+      return;
+    }
+    if (board_id === 'images') {
+      return imagesQueryArg;
+    } else if (board_id === 'assets') {
+      return assetsQueryArg;
+    } else if (board_id === 'no_board') {
+      return noBoardQueryArg;
+    } else {
+      return { board_id, ...baseQueryArg };
+    }
+  }, [board_id]);
+
+  const { total } = useListImagesQuery(queryArg ?? skipToken, {
+    selectFromResult: ({ currentData }) => ({ total: currentData?.total }),
+  });
+
+  return total;
+};