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/Ai.php

@@ -0,0 +1,65 @@
+<?php
+
+namespace tobimori\Seo;
+
+use Generator;
+use Kirby\Exception\Exception as KirbyException;
+use tobimori\Seo\Ai\Content;
+use tobimori\Seo\Ai\Driver;
+
+use function is_string;
+use function is_array;
+
+/**
+ * Ai facade
+ */
+class Ai
+{
+	private static array $providers = [];
+
+	public static function enabled(): bool
+	{
+		return (bool)Seo::option('ai.enabled', false);
+	}
+
+	/**
+	 * Returns a provider instance for the given ID or the default provider.
+	 */
+	public static function provider(string|null $providerId = null): Driver
+	{
+		$providerId ??= Seo::option('ai.provider');
+
+		if (isset(self::$providers[$providerId])) {
+			return self::$providers[$providerId];
+		}
+
+		$config = Seo::option("ai.providers.{$providerId}");
+		if (!is_array($config)) {
+			throw new KirbyException("AI provider \"{$providerId}\" is not defined.");
+		}
+
+		$driver = $config['driver'] ?? null;
+		if (!is_string($driver) || $driver === '') {
+			throw new KirbyException("AI provider \"{$providerId}\" is missing a driver reference.");
+		}
+
+		if (!is_subclass_of($driver, Driver::class)) {
+			throw new KirbyException("AI provider driver \"{$driver}\" must extend " . Driver::class . '.');
+		}
+
+		return self::$providers[$providerId] = new $driver($providerId);
+	}
+
+	public static function streamTask(string $taskId, array $variables = []): Generator
+	{
+		$snippet = "seo/prompts/tasks/{$taskId}";
+		$prompt = trim(snippet($snippet, $variables, return: true));
+		if ($prompt === '') {
+			throw new KirbyException("AI prompt snippet \"{$snippet}\" is missing or empty.");
+		}
+
+		$content = [Content::user()->text($prompt)];
+
+		return self::provider()->stream($content);
+	}
+}