Suppress Duplicate Alerts

An alerting pipeline fires the same alert repeatedly while a condition persists. You need to suppress duplicates: an alert with a given key should only pass through if that key has not been seen in the last `window` seconds. Implement an `AlertSuppressor` class: - `AlertSuppressor(window)` — construct with a suppression window in seconds. - `should_emit(key, now)` — return `True` if this alert should fire, `False` if it is suppressed. `now` is a monotonically non-decreasing timestamp in seconds. The trap is memory: a naive dictionary keyed by alert key grows forever on a long-running process with high-cardinality keys. Keep the bookkeeping bounded.