[Feature] Support for decentralized storage backends (Sia, via S3-compatible API / native backend)

I have searched the existing feature requests, both open and closed, to make sure this is not a duplicate request. • Yes The feature I’d like Immich to support storing the media library on [Sia]( a decentralized, end-to-end encrypted cloud storage network. Currently, Immich’s upload location has to be a local filesystem path. Users who want to keep their library on remote or decentralized storage have to rely on FUSE mounts (rclone, s3fs, etc.), which causes problems: slow thumbnail generation and library scans, fragile behavior when the mount drops, and no way for Immich to handle object-storage semantics properly. Proposed approach Storage backend abstraction. Introduce a pluggable storage layer (local FS as the default) so that originals, thumbnails, encoded videos, and other generated assets can live on different backends. S3-compatible backend as the first step. Sia’s renterd exposes an S3-compatible API, so a generic S3 backend would already enable Sia s…