refactor: extract magic constants — wave 2 (TanStack Query defaults)

Promote the duplicated query lifecycle constants in \$shared/api/queryClient.ts:

- staleTime (5 minutes) -> DEFAULT_QUERY_STALE_TIME_MS
- gcTime (10 minutes)   -> DEFAULT_QUERY_GC_TIME_MS
- retry (3)             -> QUERY_RETRY_COUNT
- retryDelay (1s base, 30s cap) -> QUERY_RETRY_BASE_DELAY_MS + QUERY_RETRY_MAX_DELAY_MS

fontCatalogStore and availableFilterStore now import the stale/gc
constants instead of re-deriving '5 * 60 * 1000' / '10 * 60 * 1000'.

fontCatalogStore.svelte.spec.ts's queryClient mock now passes through
the new named exports via importOriginal so the consumer's imports
resolve.

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

@@ -17,7 +17,11 @@
 
 import { fetchProxyFilters } from '$features/FilterAndSortFonts/api/filters/filters';
 import type { FilterMetadata } from '$features/FilterAndSortFonts/api/filters/filters';
-import { queryClient } from '$shared/api/queryClient';
+import {
+    DEFAULT_QUERY_GC_TIME_MS,
+    DEFAULT_QUERY_STALE_TIME_MS,
+    queryClient,
+} from '$shared/api/queryClient';
 import {
     type QueryKey,
     QueryObserver,
@@ -81,8 +85,8 @@ export class AvailableFilterStore {
         return {
             queryKey: this.getQueryKey(),
             queryFn: () => this.fetchFn(),
-            staleTime: 5 * 60 * 1000, // 5 minutes
-            gcTime: 10 * 60 * 1000, // 10 minutes
+            staleTime: DEFAULT_QUERY_STALE_TIME_MS,
+            gcTime: DEFAULT_QUERY_GC_TIME_MS,
         };
     }