refactor(shared/api): lazify queryClient to remove eager-construction footgun

queryClient.ts constructed the TanStack client at module eval but was not
in the sideEffects allowlist, so Rollup treated the module as pure — safe
only while a value-importer keeps it alive (D-3).

- replace the eager `queryClient` singleton with a memoized getQueryClient()
  factory; construction is deferred to first call
- the module is now genuinely side-effect-free, so no sideEffects exception
  is needed and construction can never be legally tree-shaken away
- route all consumers through getQueryClient() (QueryProvider as first
  caller; stores via class fields/observers; tests via a local alias; the
  fontCatalogStore spec mock now overrides getQueryClient)

src/widgets/ComparisonView/model/stores/comparisonStore.test.ts

@@ -11,7 +11,9 @@
 
 import type { UnifiedFont } from '$entities/Font';
 import { UNIFIED_FONTS } from '$entities/Font/testing';
-import { queryClient } from '$shared/api/queryClient';
+import { getQueryClient } from '$shared/api/queryClient';
+
+const queryClient = getQueryClient();
 import {
     beforeEach,
     describe,