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>

composer.json

@@ -10,6 +10,8 @@
         "doctrine/doctrine-bundle": "^3.2",
         "doctrine/doctrine-migrations-bundle": "^4.0",
         "doctrine/orm": "^3.6",
+        "league/flysystem-aws-s3-v3": "*",
+        "league/flysystem-bundle": "*",
         "pentatrion/vite-bundle": "^8.2",
         "phpdocumentor/reflection-docblock": "^6.0",
         "phpstan/phpdoc-parser": "^2.3",