feat: Provisionner automatiquement un nouvel établissement

Lorsqu'un super-admin crée un établissement via l'interface, le système
doit automatiquement créer la base tenant, exécuter les migrations,
créer le premier utilisateur admin et envoyer l'invitation — le tout
de manière asynchrone pour ne pas bloquer la réponse HTTP.

Ce mécanisme rend chaque établissement opérationnel dès sa création
sans intervention manuelle sur l'infrastructure.

backend/src/Scolarite/Infrastructure/Storage/S3FileStorage.php

@@ -0,0 +1,91 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Scolarite\Infrastructure\Storage;
+
+use App\Scolarite\Application\Port\FileStorage;
+use Aws\S3\S3Client;
+
+use function is_resource;
+
+use League\Flysystem\AwsS3V3\AwsS3V3Adapter;
+use League\Flysystem\Filesystem;
+use League\Flysystem\UnableToDeleteFile;
+use League\Flysystem\UnableToReadFile;
+use Override;
+use Psr\Log\LoggerInterface;
+use Psr\Log\NullLogger;
+use RuntimeException;
+
+use function sprintf;
+
+final readonly class S3FileStorage implements FileStorage
+{
+    private Filesystem $filesystem;
+    private LoggerInterface $logger;
+
+    public function __construct(
+        string $endpoint,
+        string $bucket,
+        string $key,
+        string $secret,
+        string $region,
+        ?LoggerInterface $logger = null,
+    ) {
+        $this->logger = $logger ?? new NullLogger();
+        $client = new S3Client([
+            'endpoint' => $endpoint,
+            'credentials' => [
+                'key' => $key,
+                'secret' => $secret,
+            ],
+            'region' => $region,
+            'version' => 'latest',
+            'use_path_style_endpoint' => true,
+        ]);
+
+        $this->filesystem = new Filesystem(
+            new AwsS3V3Adapter($client, $bucket),
+        );
+    }
+
+    #[Override]
+    public function upload(string $path, mixed $content, string $mimeType): string
+    {
+        $config = [
+            'ContentType' => $mimeType,
+        ];
+
+        if (is_resource($content)) {
+            $this->filesystem->writeStream($path, $content, $config);
+        } else {
+            $this->filesystem->write($path, (string) $content, $config);
+        }
+
+        return $path;
+    }
+
+    #[Override]
+    public function delete(string $path): void
+    {
+        try {
+            $this->filesystem->delete($path);
+        } catch (UnableToDeleteFile $e) {
+            $this->logger->warning('S3 delete failed, possible orphan blob: {path}', [
+                'path' => $path,
+                'error' => $e->getMessage(),
+            ]);
+        }
+    }
+
+    #[Override]
+    public function readStream(string $path): mixed
+    {
+        try {
+            return $this->filesystem->readStream($path);
+        } catch (UnableToReadFile $e) {
+            throw new RuntimeException(sprintf('Impossible de lire le fichier : %s', $path), 0, $e);
+        }
+    }
+}