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/Sitemap/Sitemap.php

@@ -0,0 +1,87 @@
+<?php
+
+namespace tobimori\Seo\Sitemap;
+
+use DOMDocument;
+use Kirby\Cms\App;
+use Kirby\Toolkit\Collection;
+
+class Sitemap extends Collection
+{
+	public function __construct(protected string $key, array $data = [], bool $caseSensitive = false)
+	{
+		parent::__construct($data, $caseSensitive);
+	}
+
+	public function key(): string
+	{
+		return $this->key;
+	}
+
+	public function loc(): string
+	{
+		return kirby()->site()->canonicalFor('sitemap-' . $this->key . '.xml');
+	}
+
+	public function lastmod(): string
+	{
+		$lastmod = 0;
+		foreach ($this as $url) {
+			$lastmod = max($lastmod, strtotime($url->lastmod()));
+		}
+
+		if ($lastmod > 0) {
+			return date('c', $lastmod);
+		}
+
+		return date('c');
+	}
+
+	public function createUrl(string $loc): SitemapUrl
+	{
+		$url = $this->makeUrl($loc);
+		$this->append($url);
+		return $url;
+	}
+
+	public static function makeUrl(string $url): SitemapUrl
+	{
+		return new SitemapUrl($url);
+	}
+
+	public function toDOMNode(DOMDocument $doc = new DOMDocument('1.0', 'UTF-8'))
+	{
+		$doc->formatOutput = true;
+
+		$root = $doc->createElement('sitemap');
+		foreach (['loc', 'lastmod'] as $key) {
+			$root->appendChild($doc->createElement($key, $this->$key()));
+		}
+
+		return $root;
+	}
+
+	public function toString(): string
+	{
+		$doc = new DOMDocument('1.0', 'UTF-8');
+		$doc->formatOutput = true;
+
+		$stylesheetUrl = App::instance()->url() . '/sitemap.xsl';
+		$doc->appendChild($doc->createProcessingInstruction('xml-stylesheet', 'type="text/xsl" href="' . $stylesheetUrl . '"'));
+
+		$root = $doc->createElementNS('http://www.sitemaps.org/schemas/sitemap/0.9', 'urlset');
+		$root->setAttributeNS('http://www.w3.org/2000/xmlns/', 'xmlns:xhtml', 'http://www.w3.org/1999/xhtml');
+
+		// version can be null when installing branches during development
+		if ($version = App::plugin('tobimori/seo')->version()) {
+			$root->setAttribute('seo-version', $version);
+		}
+
+		foreach ($this as $url) {
+			$root->appendChild($url->toDOMNode($doc));
+		}
+
+		$doc->appendChild($root);
+		return $doc->saveXML();
+	}
+}