feat(version-check): add in-app update prompt with Remote Config

Adds a production-grade in-app version check that prompts users to update when a new build is available. Soft updates are dismissable. Force updates block the app entirely. Configured via FirebaseRemote Config so rollouts can be triggered without redeploying.

- Sealed result types (NoUpdate / SoftUpdate / ForceUpdate) for type-safe pattern matching
- AppVersionCheckService
- AppUpdateGate widget encapsulates listener, route guard and dialog wireup, isolated from save_family_app
- Serialized notifier operations prevent race between dismiss and refresh, mounted checks blindar disposal edge cases                                                                                                  - Build-aware dismiss persistence via SharedPreferences

packages/sf_localizations/assets/l10n/de.json

@@ -857,5 +857,11 @@
   "videoCall": "Videoanruf",
   "watchesOnMap": "Smartwatches auf der Karte:",
   "wifiSettings": "WLAN-Einstellungen",
-  "yesterday": "Gestern"
+  "yesterday": "Gestern",
+  "appUpdateAvailableTitle": "Update verfügbar",
+  "appUpdateAvailableMessage": "Eine neue Version von SaveFamily ist verfügbar.",
+  "appUpdateRequiredTitle": "Update erforderlich",
+  "appUpdateRequiredMessage": "Du musst SaveFamily aktualisieren, um die App weiterhin zu nutzen.",
+  "appUpdateLater": "Später",
+  "appUpdateNow": "Jetzt aktualisieren"
 }

packages/sf_localizations/assets/l10n/en.json

@@ -857,5 +857,11 @@
   "renewCardPinTitle": "Enter your security PIN to renew the card",
   "renewCardSuccess": "Card renewed successfully",
   "renewCardError": "Error renewing card",
-  "passwordLabel": "Password (6 to 12 characters)"
+  "passwordLabel": "Password (6 to 12 characters)",
+  "appUpdateAvailableTitle": "Update available",
+  "appUpdateAvailableMessage": "A new version of SaveFamily is available.",
+  "appUpdateRequiredTitle": "Update required",
+  "appUpdateRequiredMessage": "You need to update SaveFamily to keep using the app.",
+  "appUpdateLater": "Later",
+  "appUpdateNow": "Update now"
 }

packages/sf_localizations/assets/l10n/es.json

@@ -857,5 +857,11 @@
   "renewCardTokenHint": "Introduce el código de la nueva tarjeta",
   "renewCardPinTitle": "Introduce tu PIN de seguridad para renovar la tarjeta",
   "renewCardSuccess": "Tarjeta renovada correctamente",
-  "renewCardError": "Error al renovar la tarjeta"
+  "renewCardError": "Error al renovar la tarjeta",
+  "appUpdateAvailableTitle": "Actualización disponible",
+  "appUpdateAvailableMessage": "Hay una nueva versión de SaveFamily disponible.",
+  "appUpdateRequiredTitle": "Actualización requerida",
+  "appUpdateRequiredMessage": "Necesitas actualizar SaveFamily para seguir usando la app.",
+  "appUpdateLater": "Más tarde",
+  "appUpdateNow": "Actualizar ahora"
 }

packages/sf_localizations/assets/l10n/fr.json

@@ -857,5 +857,11 @@
   "videoCall": "Appel vidéo",
   "watchesOnMap": "Montres connectées sur la carte :",
   "wifiSettings": "Paramètres WiFi",
-  "yesterday": "Hier"
+  "yesterday": "Hier",
+  "appUpdateAvailableTitle": "Mise à jour disponible",
+  "appUpdateAvailableMessage": "Une nouvelle version de SaveFamily est disponible.",
+  "appUpdateRequiredTitle": "Mise à jour requise",
+  "appUpdateRequiredMessage": "Vous devez mettre à jour SaveFamily pour continuer à utiliser l'application.",
+  "appUpdateLater": "Plus tard",
+  "appUpdateNow": "Mettre à jour maintenant"
 }

packages/sf_localizations/assets/l10n/it.json

@@ -857,5 +857,11 @@
   "videoCall": "Videochiamata",
   "watchesOnMap": "Smartwatch sulla mappa:",
   "wifiSettings": "Impostazioni WiFi",
-  "yesterday": "Ieri"
+  "yesterday": "Ieri",
+  "appUpdateAvailableTitle": "Aggiornamento disponibile",
+  "appUpdateAvailableMessage": "È disponibile una nuova versione di SaveFamily.",
+  "appUpdateRequiredTitle": "Aggiornamento richiesto",
+  "appUpdateRequiredMessage": "Devi aggiornare SaveFamily per continuare a usare l'app.",
+  "appUpdateLater": "Più tardi",
+  "appUpdateNow": "Aggiorna ora"
 }

packages/sf_localizations/assets/l10n/pt.json

@@ -857,5 +857,11 @@
   "videoCall": "Videochamada",
   "watchesOnMap": "Relógios inteligentes no mapa:",
   "wifiSettings": "Configurações WiFi",
-  "yesterday": "Ontem"
+  "yesterday": "Ontem",
+  "appUpdateAvailableTitle": "Atualização disponível",
+  "appUpdateAvailableMessage": "Há uma nova versão do SaveFamily disponível.",
+  "appUpdateRequiredTitle": "Atualização necessária",
+  "appUpdateRequiredMessage": "Precisas atualizar o SaveFamily para continuar a usar a app.",
+  "appUpdateLater": "Mais tarde",
+  "appUpdateNow": "Atualizar agora"
 }