Initiates a new upload using the TUS protocol. This endpoint creates an upload session and returns the URL where file chunks should be sent.

Required Metadata:
All metadata fields must be base64 encoded and sent in the Upload-Metadata header.

• authorization: Authentication token
• bucket_id: UUID of the bucket where the file will be stored
• filename: File name
• filetype: MIME type of the file

Optional Metadata:

• folder_id: UUID of the folder where the file will be stored
• type: File category (video, audio, image, document, archive, other)