feat: install Flysystem S3 and configure SeaweedFS storage

Add league/flysystem-bundle and league/flysystem-aws-s3-v3 packages and
configure the default.storage adapter to use AWS S3Client pointed at the
SeaweedFS endpoint (s3.lclr.dev) with path-style endpoints and secret-based
credentials.

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

config/bundles.php

@@ -15,4 +15,5 @@ return [
     Symfony\Bundle\MakerBundle\MakerBundle::class => ['dev' => true],
     Symfony\UX\React\ReactBundle::class => ['all' => true],
     Pentatrion\ViteBundle\PentatrionViteBundle::class => ['all' => true],
+    League\FlysystemBundle\FlysystemBundle::class => ['all' => true],
 ];