feat: auto-create MinIO bucket and validate storage in development

Add a separate minio-init container that automatically creates the 'local'
bucket when MinIO starts in development. Mark the seeded S3Storage as usable
by default so developers can use MinIO without manual validation.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

database/seeders/S3StorageSeeder.php

@@ -20,6 +20,7 @@ class S3StorageSeeder extends Seeder
             'bucket' => 'local',
             'endpoint' => 'http://coolify-minio:9000',
             'team_id' => 0,
+            'is_usable' => true,
         ]);
     }
 }