fix: preserve live Nginx entry when saved draft differs

frontend/src/locales/en-US.json

@@ -902,6 +902,7 @@
     "saveDomain": "Save domain",
     "restartRequired": "Gateway mode saved; switching between Go and Nginx requires restarting the management service",
     "siteActivationRequired": "Entry saved; prepare and enable the Nginx site below for first use",
+    "pendingEntry": "Nginx still serves {address}; save to validate and apply the new entry",
     "applied": "Public entry updated; Nginx configuration is active",
     "saveFailed": "Could not save domain",
     "dns": "DNS",