Update the Gofile backend to use the new direct upload endpoint based on the latest API changes.
The previous implementation used dynamic server selection, but Gofile has simplified their API
to use a single upload endpoint at https://upload.gofile.io/uploadfile.
This change:
- Removes server selection logic and related code
- Simplifies the Fs struct by removing server-related fields
- Updates the upload process to use the direct upload URL
