fix(shell): auth-rejected hub no longer reported as unreachable

The sustained-failure banner treated every failed health poll as
'can't reach the hub'. With token auth active, a wrong or rotated
token gets UNAUTHENTICATED from a perfectly reachable hub — the
old wording sent the operator to fix the endpoint. The shell now
uses the SDK's probe() and, on auth rejection, switches the banner
to 'rejected the sign-in — check the access token' (key-off icon,
DE+EN). Two widget tests pin the wording per failure kind and the
banner clearing once the probe turns serving.

Signed-off-by: flemming-it <stefan.a.flemming@googlemail.com>

lib/l10n/app_de.arb

@@ -1671,6 +1671,12 @@
     }
   },
   "hubUnreachableOpenSettings": "Einstellungen öffnen",
+  "hubAuthRejectedBanner": "{endpoint} lehnt die Anmeldung ab — Zugriffstoken prüfen",
+  "@hubAuthRejectedBanner": {
+    "placeholders": {
+      "endpoint": {"type": "String"}
+    }
+  },
   "navFederation": "Föderation",
   "federationTitle": "Föderation",
   "federationReloadTooltip": "Satelliten neu laden",

lib/l10n/app_en.arb

@@ -1695,6 +1695,12 @@
     }
   },
   "hubUnreachableOpenSettings": "Open Settings",
+  "hubAuthRejectedBanner": "{endpoint} rejected the sign-in — check the access token",
+  "@hubAuthRejectedBanner": {
+    "placeholders": {
+      "endpoint": {"type": "String"}
+    }
+  },
   "navFederation": "Federation",
   "federationTitle": "Federation",
   "federationReloadTooltip": "Reload satellites",

lib/l10n/app_localizations.dart

@@ -4903,6 +4903,12 @@ abstract class AppLocalizations {
   /// **'Open Settings'**
   String get hubUnreachableOpenSettings;
 
+  /// No description provided for @hubAuthRejectedBanner.
+  ///
+  /// In en, this message translates to:
+  /// **'{endpoint} rejected the sign-in — check the access token'**
+  String hubAuthRejectedBanner(String endpoint);
+
   /// No description provided for @navFederation.
   ///
   /// In en, this message translates to:

lib/l10n/app_localizations_de.dart

@@ -2890,6 +2890,11 @@ class AppLocalizationsDe extends AppLocalizations {
   @override
   String get hubUnreachableOpenSettings => 'Einstellungen öffnen';
 
+  @override
+  String hubAuthRejectedBanner(String endpoint) {
+    return '$endpoint lehnt die Anmeldung ab — Zugriffstoken prüfen';
+  }
+
   @override
   String get navFederation => 'Föderation';
 

lib/l10n/app_localizations_en.dart

@@ -2891,6 +2891,11 @@ class AppLocalizationsEn extends AppLocalizations {
   @override
   String get hubUnreachableOpenSettings => 'Open Settings';
 
+  @override
+  String hubAuthRejectedBanner(String endpoint) {
+    return '$endpoint rejected the sign-in — check the access token';
+  }
+
   @override
   String get navFederation => 'Federation';