fix: Fix undefined query data and add fallback to Fontshare API

- Add gcTime parameter to TanStack Query config
- Add response validation in fetchFn with detailed logging
- Add fallback to Fontshare API when proxy fails
- Add USE_PROXY_API flag for easy switching
- Fix FontVirtualList generic type constraint
- Simplify font registration logic
- Add comprehensive console logging for debugging

Fixes: Query data cannot be undefined error

src/entities/Font/ui/FontVirtualList/FontVirtualList.svelte

@@ -3,7 +3,7 @@
     - Renders a virtualized list of fonts
     - Handles font registration with the manager
 -->
-<script lang="ts" generics="T extends ({ id: string } | [{ id: string }, { id: string }])">
+<script lang="ts" generics="T extends { id: string }">
 import { VirtualList } from '$shared/ui';
 import type { ComponentProps } from 'svelte';
 import { appliedFontsManager } from '../../model';
@@ -16,12 +16,7 @@ let { items, children, onVisibleItemsChange, ...rest }: Props = $props();
 
 function handleInternalVisibleChange(visibleItems: T[]) {
     // Auto-register fonts with the manager
-    const slugs = visibleItems.map(item => {
-        if (Array.isArray(item)) {
-            return item.map(font => font.id);
-        }
-        return item.id;
-    }).flat();
+    const slugs = visibleItems.map(item => item.id);
     appliedFontsManager.registerFonts(slugs);
 
     // Forward the call to any external listener