`tsc -b` in the Docker image build failed on every non-en locale
(TS2739: gatewayStrip missing degraded, heartbeatStale) because the new
keys were declared required on Translations. The web locales are full
objects, not partial overrides, so a new key must be optional and read
through the `en` fallback — the pattern the existing 102 optional keys
(loadFailed, gateway, gatewayHint, ...) already use.
Before: web `tsc -b` -> 16 x TS2739. After: 0 locale errors.
f96258d481