Task d25b875f: Last-good snapshot cache and staleness handling (#170)

custom_components/nestquest/strings.json

@@ -23,6 +23,7 @@
           "horizon_days": "Generation horizon (days)",
           "day_rollover_time": "Day rollover time (HH:MM)",
           "panel_idle_timeout": "Panel idle timeout (seconds)",
+          "snapshot_staleness": "Last-good snapshot staleness (seconds)",
           "api_base_url": "NestQuest API base URL (http://host:port)",
           "panel_token": "Panel service token",
           "admin_user_ids": "Admin users (parents)"
@@ -33,6 +34,7 @@
       "invalid": "Invalid value.",
       "invalid_time": "Time must use 24-hour HH:MM format.",
       "invalid_url": "Enter the API base URL as a full http:// or https:// URL with a host.",
+      "invalid_staleness": "Last-good snapshot staleness must be at least the update interval.",
       "no_admins": "Select at least one admin user; an empty allowlist would lock everyone out.",
       "invalid_admin": "Invalid admin selection."
     }