refactor(fontCatalogStore): single source of truth for query params

On initial load, two separate $effects in bindings.svelte.ts — one for
filters, one for sort — each issued its own setOptions with a different
queryKey on the first flush, producing an orphaned
`/fonts?limit=50&offset=0` request immediately followed by the real
`/fonts?limit=50&sort=popularity&offset=0`. Hardcoding the default sort
on the singleton would have papered over the symptom while leaving the
sortStore default and the catalog-store default coupled by hand.

Make bindings the sole emitter of query params:

- features/.../bindings: merge filter + sort effects into one. The effect
  reads both stores, builds the merged param object, and issues a single
  setParams. No more interleaved setOptions on mount.
- entities/.../fontCatalogStore: gate the observer with `enabled: false`
  on construction. The first setParams flips `#enabled` on and triggers
  exactly one fetch with the correct queryKey. Removes the need for a
  hardcoded default sort on the singleton.
- isEmpty is also gated on `#enabled` so the brief pre-config window
  doesn't render "no results" before bindings configures the query.
- The constructor seeds #result from observer.getCurrentResult() because
  subscribe may not fire synchronously when the observer is disabled.

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

@@ -42,20 +42,19 @@ $effect.root(() => {
     });
 
     /**
-     * Mirror filter selections + debounced search query into fontCatalogStore params.
+     * Mirror filter selections + debounced search query + sort into fontCatalogStore params.
+     *
+     * Filters and sort are merged into one setParams call to avoid a startup race:
+     * two separate effects each issued setOptions with a different queryKey on the
+     * first flush, producing an orphaned `?limit=50&offset=0` fetch immediately
+     * followed by the real `?limit=50&sort=popularity&offset=0` fetch.
+     *
      * untrack the write so fontCatalogStore's internal $state reads don't feed back
      * into this effect's dependency graph.
      */
     $effect(() => {
         const params = mapAppliedFiltersToParams(appliedFilterStore);
-        untrack(() => fontCatalogStore.setParams(params));
-    });
-
-    /**
-     * Mirror sort selection into fontCatalogStore.
-     */
-    $effect(() => {
-        const apiSort = sortStore.apiValue;
-        untrack(() => fontCatalogStore.setSort(apiSort));
+        const sort = sortStore.apiValue;
+        untrack(() => fontCatalogStore.setParams({ ...params, sort }));
     });
 });