Both example files pointed at the old CALENDAR_ENCRYPTION_KEY name, and
.env.example did not mention the key at all. Since compose now aborts
startup when it is unset, anyone setting up a fresh install from these
templates hit a failure the templates never explained.
Adds the current variable name, the generation command, and a note that
losing the value makes stored credentials unrecoverable.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
schalli