`t()` answers a missing key with the key, so "does this code have a
sentence" was a comparison written inline at every site that wanted a
code's sentence or a fallback, twenty-odd times in several spellings.
translateOrNull, translateCodeOrNull and translateCode in
src/lib/i18n/translate-code.ts now hold that probe, every site uses
them, and a guard refuses the inline comparison anywhere else.
The admin test response carried a code and status per channel that nothing rendered. The toast now lists each failing channel with the translated cause and the HTTP status or SMTP code. The relay reply is no longer part of that response, and the ntfy error no longer echoes the topic, which the sender treats as a secret.
Refs #947
Marc-André Bombeck