fix(links): use plus icon for logo upload placeholder

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

inc/helpers/jio-links.php

@@ -514,7 +514,7 @@ if (!function_exists('jio_submit_links_modal')) :
 					. '<div class="form-select"><select name="link_category" class="form-control">' . $cats_options . '</select></div></div>'
 				: '';
 
-			$placeholder_upload = get_template_directory_uri() . '/assets/img/placeholder.svg';
+			$placeholder_upload = get_template_directory_uri() . '/assets/icons/upload-add.svg';
 			$body .= '<form class="form-horizontal mt10 jio-links-submit-form" action="' . esc_url(admin_url('admin-ajax.php')) . '" method="post" enctype="multipart/form-data">';
 			$body .= '<div class="row gutters-5">';
 			$body .= '<div class="col-sm-6 mb10"><div class="em09 muted-2-color mb6">' . esc_html__('网站名称（必填）', 'jio') . '</div>'

tests/widget-system/links-page-contract.test.cjs

@@ -22,6 +22,7 @@ test('native links are the only friend-link store', () => {
   assert.match(template, /jio_page_links_html\(/)
   assert.match(template, /jio_submit_links_modal\(/)
   assert.match(helper, /get_bookmarks\(/)
+  assert.match(helper, /assets\/icons\/upload-add\.svg/)
 })
 
 test('the retired friend-link option and admin REST surface stay gone', () => {