Version 0.19.0

Added credit payment for large files: a file above 64 MiB can now be paid with credits, split into pieces and saved as one file.

A large file used to need a wallet even when the account held enough credits. Now each piece is paid for and uploaded under our payment, and the pieces are recorded as one file at the end. Two ceilings apply and are shown before you confirm — 2,048 credits per file and 4,096 credits per account per day; past a ceiling, the wallet is the way. The term stays fixed at 28 days and cannot be extended.

Added a warning where credit payment is chosen: credit-bought storage cannot be extended, so pick a generous term from your wallet for anything you need longer.