New adminalert worker polls for feedback + word complaints arriving since the last check
and coalesces a burst into one digest email per interval (5 min), inert unless a distinct
admin sender (BACKEND_SMTP_ADMIN_FROM) and recipient (BACKEND_ADMIN_EMAIL, comma-separated
allowed) are configured. The mailer gains a per-message From override and splits a
comma-separated To into separate recipients (go-mail needs them as a list). Feedback/game
stores gain CountSince/CountComplaintsSince. Unit tests cover the digest, the skip-when-
empty, and the recipient split.
Ilia Denisov