[ HiveTalk/swarm ] feat: Add S3/Tigris storage backend for Blossom media - Add s3storage.go with StoreBlob, LoadBlob, DeleteBlob, ListBlobs - Support dual storage: filesystem (default) or S3 via STORAGE_BACKEND env - Add AWS SDK v2 dependencies for S3-compatible storage - Update Dockerfile and docker-compose.yml with S3 env variables - Add S3 configuration docs to .env.example - Add unit tests for S3 storage functions - Remove broken standalone test programs from tests/