refactor(shared): keep BaseQueryStore out of the lib barrels

BaseQueryStore pulls @tanstack/query-core. Re-exporting it through the
broad $shared/lib and $shared/lib/helpers barrels made every consumer of
those barrels eager-load TanStack at module-eval time (no tree-shaking in
vitest/vite-node), which is what surfaced the queryClient mock init-order
failure. Its single consumer now imports it by path.

src/entities/Font/model/store/fontsByIdsStore/fontsByIdsStore.svelte.ts

@@ -1,5 +1,5 @@
 import { fontKeys } from '$shared/api/queryKeys';
-import { BaseQueryStore } from '$shared/lib';
+import { BaseQueryStore } from '$shared/lib/helpers/BaseQueryStore/BaseQueryStore.svelte';
 import {
     fetchFontsByIds,
     seedFontCache,