ConfigController::get and HeartbeatController::post verified HMAC but never
checked nonce replay or timestamp freshness, so a captured signed request
(e.g. a replayed heartbeat) could be replayed forever, masking a dead
device. Inject NonceRepository (+Config) into both and add the same
timestamp-window + nonce-remember checks IngestController already applies,
after HMAC verification and before the response/side effect.
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