Version 0.51.0

Added a Try again button beside a failed download — but only where trying again can actually work.

Fixed what you are told when a download does not work: it said it in English, with internal identifiers in it, and offered no way to try again.

A failed download printed the error exactly as the code raised it, which in a Korean session meant an English sentence with the file's internal storage id and the address of the server that was tried. Worse, closing the browser's save dialog produced the same shape, so choosing not to save read as a failure. NMTS now judges what went wrong and says it in your language, differently for each case: a file the storage network does not have says so and does not pretend that pressing again will help, while not reaching the network says that instead and gives you a Try again button. The same judgement now covers uploads, which had the same problem.