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/shared/lib/helpers/BaseQueryStore/BaseQueryStore.svelte.ts

@@ -1,4 +1,4 @@
-import { queryClient } from '$shared/api/queryClient';
+import { getQueryClient } from '$shared/api/queryClient';
 import {
     QueryObserver,
     type QueryObserverOptions,
@@ -20,7 +20,7 @@ export abstract class BaseQueryStore<TData, TError = Error> {
     #unsubscribe: () => void;
 
     constructor(options: QueryObserverOptions<TData, TError, TData, any, any>) {
-        this.#observer = new QueryObserver(queryClient, options);
+        this.#observer = new QueryObserver(getQueryClient(), options);
         this.#unsubscribe = this.#observer.subscribe(result => {
             this.#result = result;
         });

src/shared/lib/helpers/BaseQueryStore/BaseQueryStore.test.ts

@@ -1,4 +1,6 @@
-import { queryClient } from '$shared/api/queryClient';
+import { getQueryClient } from '$shared/api/queryClient';
+
+const queryClient = getQueryClient();
 import {
     beforeEach,
     describe,