Devlog #9: Object storage for media files

Storing video files on a server's local disk is a bad idea. The disk fills up, there might be a single server, backup is complicated. We use object storage with an S3-compatible API.

The core principle: files in object storage are identified by a key, and in the database we store only that key. The actual video is in the storage, in the database — only metadata.

File lifecycle: uploaded by user → stored in object storage → transferred to TikTok API → after publication confirmation it can be deleted. We don't store video indefinitely — this saves costs and keeps things clean.

Presigned URLs allow giving temporary access to a file without permanent credentials — this is convenient for UI previews.