chore: update kirby-seo plugin to v2.0.0-alpha.12

Update plugin from v1.1.2 to v2.0.0-alpha.12 for Kirby 5 compatibility.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

site/plugins/kirby-seo/snippets/prompts/meta.php

@@ -0,0 +1,28 @@
+<?php
+
+/** @var \Kirby\Cms\Page $page
+ ** @var \Kirby\Cms\Site $site
+ ** @var string|null $currentField */
+
+$meta = $page->metadata();
+$currentField = $currentField ?? null;
+
+$metaFields = [
+	'metaTitle' => 'Meta Title',
+	'metaDescription' => 'Meta Description',
+	'ogTitle' => 'Open Graph Title',
+	'ogDescription' => 'Open Graph Description'
+];
+?>
+
+<existing-metadata>
+<?php foreach ($metaFields as $key => $label) : ?>
+<?php
+	$value = $meta->get($key);
+	if ($currentField === $key || !$value || $value === '') {
+		continue;
+	}
+	?>
+	<<?= $key ?>><?= $value ?></<?= $key ?>>
+<?php endforeach ?>
+</existing-metadata>