Add more no-registration upload sites

[j0rd1s3rr4n0]

Summary

• Adds five more no-registration providers: file.io, Uguu, Catbox, Litterbox, and transfer.sh.
• Normalizes JSON, plain-text, multipart, and PUT upload responses into UploadResult.
• Registers the providers for CLI, GUI, and TUI discovery.
• Updates README and interface docs with the new services.

Validation

• python -m unittest discover -s tests
• python -m py_compile on package modules and launchers
• python -m fileuploader_cli --no-banner services --active-only
• python -m fileuploader_cli services --json
• Tkinter GUI smoke construction
• TUI service table smoke check

Closes #36.