fix: Address issues with all 4 features

1. Admin Store Link - Add to WP admin bar (Menu.php) with proper option check
2. Activity Log - Fix Loading text to show correct state after data loads
3. Avatar Upload - Use correct option key woonoow_allow_custom_avatar
4. Downloadable Files - Connect to WooCommerce native:
   - Add downloads array to format_product_full
   - Add downloads/download_limit/download_expiry handling in update_product
   - Add downloads handling in create_product

admin-spa/src/routes/Settings/Notifications/ActivityLog.tsx

@@ -143,7 +143,11 @@ export default function ActivityLog() {
                     <CardHeader>
                         <CardTitle>{__('Recent Activity')}</CardTitle>
                         <CardDescription>
-                            {data?.total ? `${data.total} ${__('notifications found')}` : __('Loading...')}
+                            {isLoading
+                                ? __('Loading...')
+                                : data?.total
+                                    ? `${data.total} ${__('notifications found')}`
+                                    : __('No notifications recorded yet')}
                         </CardDescription>
                     </CardHeader>
                     <CardContent>