refactor(GetFonts): consolidate filtersStore wiring into bindings

Move the filtersStore → filterManager.setGroups $effect.root out of
manager.svelte.ts into bindings.svelte.ts so all cross-store reactive
wiring for the feature lives in one place. manager.svelte.ts now only
constructs and exports the singleton.

src/features/GetFonts/model/state/bindings.svelte.ts

@@ -13,9 +13,34 @@ import { fontStore } from '$entities/Font';
 import { untrack } from 'svelte';
 import { mapManagerToParams } from '../../lib/mapper/mapManagerToParams';
 import { sortStore } from '../store/sortStore.svelte';
+import { filtersStore } from './filters.svelte';
 import { filterManager } from './manager.svelte';
 
 $effect.root(() => {
+    /**
+     * Populate filterManager groups when backend filter metadata resolves.
+     * filtersStore is async; until it loads, filterManager has empty groups
+     * and the UI renders nothing for them.
+     */
+    $effect(() => {
+        const dynamicFilters = filtersStore.filters;
+
+        if (dynamicFilters.length > 0) {
+            filterManager.setGroups(
+                dynamicFilters.map(filter => ({
+                    id: filter.id,
+                    label: filter.name,
+                    properties: filter.options.sort((a, b) => b.count - a.count).map(opt => ({
+                        id: opt.id,
+                        name: opt.name,
+                        value: opt.value,
+                        selected: false,
+                    })),
+                })),
+            );
+        }
+    });
+
     /**
      * Mirror filter selections + debounced search query into fontStore params.
      * untrack the write so fontStore's internal $state reads don't feed back