Fix pre-existing eslint unused-import errors to pass script/checks gate
Remove 20 no-unused-vars violations across 5 files:
- src/actions.ts: unused Subscription type import, getCronExpression
- src/alert.ts: unused cron-parser and @welshman/lib imports
- src/digest.ts: unused now, nth, nthEq, dateToSeconds, getIdFilters,
getReplyFilters, Loader, AdapterContext, makeLoader, SocketAdapter,
call, loadRelaySelections
- src/env.ts: unused netContext import
- src/worker/email.ts: assigned-but-unused purgeJob variable
These were pre-existing errors unrelated to the web UI removal.
2fb738981e