feat: intégration plugin Kirby SEO

- Ajout de tobimori/kirby-seo via Composer
- snippet('seo/head') dans header.php (remplace les meta manuels)
- snippet('seo/schemas') dans footer.php pour JSON-LD
- Onglet SEO ajouté dans site.yml et tous les blueprints de pages
- Configuration SEO dans config.php (sitemap, robots, canonicalBase TODO)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

site/plugins/kirby-seo/classes/Dialogs/UtmShareDialog.php

@@ -0,0 +1,39 @@
+<?php
+
+namespace tobimori\Seo\Dialogs;
+
+use Kirby\Cms\App;
+use Kirby\Cms\Find;
+use Kirby\Cms\Page;
+use Kirby\Cms\Site;
+
+class UtmShareDialog
+{
+	protected Page|Site $model;
+
+	public function __construct(string $path)
+	{
+		$kirby = App::instance();
+
+		if ($path === 'site') {
+			$this->model = $kirby->site();
+		} else {
+			$id = preg_replace('/^pages\//', '', $path);
+			$this->model = Find::page($id);
+		}
+	}
+
+	public function load(): array
+	{
+		$url = $this->model instanceof Site
+			? $this->model->homePage()->url()
+			: $this->model->url();
+
+		return [
+			'component' => 'k-seo-utm-share-dialog',
+			'props' => [
+				'pageUrl' => $url
+			]
+		];
+	}
+}