Forward-port of the release/5.1 fix (9ac7df976). buildAlertsDiagnostic
previously emitted only cooldown/grouping flags, so triaging support
cases like #1341 where a user suspects an override key mismatch
required asking them to paste alerts config from inside their
container. Add an Overrides slice that names each persisted key with
its thresholds and disabled flags. Sanitize mode in the frontend
redacts the keys to override-N while keeping thresholds visible.
rcourtman
cd278bf5e2