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>

symfony.lock

@@ -35,6 +35,19 @@
             "migrations/.gitignore"
         ]
     },
+    "league/flysystem-bundle": {
+        "version": "3.6",
+        "recipe": {
+            "repo": "github.com/symfony/recipes",
+            "branch": "main",
+            "version": "1.0",
+            "ref": "913dc3d7a5a1af0d2b044c5ac3a16e2f851d7380"
+        },
+        "files": [
+            "config/packages/flysystem.yaml",
+            "var/storage/.gitignore"
+        ]
+    },
     "pentatrion/vite-bundle": {
         "version": "8.2",
         "recipe": {