refactor(font): expose stores via model segment, not the top barrel

Re-exporting the store singletons (fontCatalogStore, fontLifecycleManager,
FontsByIdsStore) through entities/Font/index.ts meant every consumer of the
barrel eager-instantiated stores and pulled @tanstack/query-core — in dev,
test, and as retained code. Drop the store re-export from the top barrel;
keep the pure surface (types, constants, domain, lib, ui) there for
convenience. Consumers that need stores import $entities/Font/model.
Aligns with the BaseQueryStore carve-out: barrel by default, segment path
when it would drag a heavy or side-effectful dependency.

src/features/FilterAndSortFonts/model/store/bindings.svelte.ts

@@ -9,7 +9,7 @@
  * observer, so it lives at module scope, not in any individual widget.
  */
 
-import { fontCatalogStore } from '$entities/Font';
+import { fontCatalogStore } from '$entities/Font/model';
 import { untrack } from 'svelte';
 import { mapAppliedFiltersToParams } from '../../lib/mapper/mapAppliedFiltersToParams';
 import { appliedFilterStore } from './appliedFilterStore/appliedFilterStore.svelte';