fix(api): mark schema-validation errors as non-retryable

The proxy returned `{fonts: null, total: 0}` for empty results, which
fetchProxyFonts surfaced as a generic Error. fontCatalogStore wrapped it
as FontNetworkError, and TanStack retried 3× with exponential backoff —
pinning the loading skeleton for ~7s before settling on an empty list.

Schema mismatches are deterministic; retrying only delays surfacing the
contract violation.

- shared/api/queryClient: introduce NonRetryableError marker class.
  The default retry handler short-circuits when it sees this so any
  store using the shared client gets fail-fast behavior for free.
- entities/Font/lib/errors: FontResponseError extends NonRetryableError.
- entities/Font/api/proxy/proxyFonts: throw FontResponseError (was a
  bare Error). Document that ProxyFontsResponse.fonts is always an array.
- entities/Font/.../fontCatalogStore.fetchPage: preserve a
  FontResponseError raised lower in the stack instead of re-wrapping
  it as FontNetworkError.
- features/FilterAndSortFonts/api/filters: throw NonRetryableError on
  invalid filters payloads and document the array-never-null contract.

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

@@ -441,6 +441,11 @@ export class FontCatalogStore {
         try {
             response = await fetchProxyFonts(params);
         } catch (cause) {
+            // Preserve non-retryable validation errors so the query client doesn't
+            // burn the retry budget on a deterministic schema mismatch.
+            if (cause instanceof FontResponseError) {
+                throw cause;
+            }
             throw new FontNetworkError(cause);
         }