The classifier settings page showed model and effort only, so the API-key
or ACP runtime could be switched only through a raw API call. It now has a
runtime select, and under ACP the provider's URL, model and prices. A PUT
carries the provider only on the ACP runtime, so the stored record stays
for a switch back. Closes#5249
A classifier settings panel under the try-out form reads and saves the model,
effort and how many requested reviews run at once through the settings route.
A save replaces all three; a refused one shows the route's reason and leaves
the form as typed. There is no API key field.