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/snippets/robots.txt.php

@@ -0,0 +1,52 @@
+<?php
+
+use Kirby\Toolkit\A;
+use tobimori\Seo\Seo;
+
+if ($content = Seo::option('robots.content')) {
+	if (is_callable($content)) {
+		$content = $content();
+	}
+
+	if (is_array($content)) {
+		$str = [];
+
+		foreach ($content as $ua => $data) {
+			$str[] = 'User-agent: ' . $ua;
+			foreach ($data as $type => $values) {
+				foreach ($values as $value) {
+					$str[] = $type . ': ' . $value;
+				}
+			}
+		}
+
+		$content = A::join($str, PHP_EOL);
+	}
+
+	echo $content;
+} else {
+	// output default
+	echo "User-agent: *\n";
+
+	$index = Seo::option('robots.index');
+
+	if ($index) {
+		echo 'Allow: /';
+		echo "\nDisallow: /panel";
+	} else {
+		echo 'Disallow: /';
+	}
+}
+
+if (($sitemap = Seo::option('robots.sitemap')) || ($sitemapModule = Seo::option('sitemap.active'))) {
+
+	// Use default sitemap if none is set
+	if (!$sitemap && $sitemapModule) {
+		$sitemap = site()->canonicalFor('/sitemap.xml', true);
+	}
+
+	// Check again, so falsy values can't be used
+	if ($sitemap) {
+		echo "\n\nSitemap: {$sitemap}";
+	}
+}