implemented comprehensive accessibility (A11y) support across the app

lib/state/app/infrastructure/loadable_state/view/loadable_state_error_bar.dart

@@ -107,16 +107,26 @@ class _LoadableStateErrorBarTextState extends State<LoadableStateErrorBarText> {
     var bloc = context.watch<LoadableStateBloc>();
     final foreground = bloc.connectionForegroundColor(context);
 
-    return Row(
-      mainAxisAlignment: MainAxisAlignment.center,
-      children: [
-        Icon(bloc.connectionIcon(), size: 14, color: foreground),
-        const SizedBox(width: 10),
-        Text(
-          bloc.connectionText(lastUpdated: widget.lastUpdated),
-          style: TextStyle(fontSize: 12, color: foreground),
+    // liveRegion, damit das Auftauchen des Offline-/Fehlerbanners angesagt wird;
+    // Row-Semantik ausgeschlossen (Icon + Text) und Text über das explizite
+    // Label getragen, sonst liest der Screenreader ihn doppelt.
+    return Semantics(
+      liveRegion: true,
+      container: true,
+      label: bloc.connectionText(lastUpdated: widget.lastUpdated),
+      child: ExcludeSemantics(
+        child: Row(
+          mainAxisAlignment: MainAxisAlignment.center,
+          children: [
+            Icon(bloc.connectionIcon(), size: 14, color: foreground),
+            const SizedBox(width: 10),
+            Text(
+              bloc.connectionText(lastUpdated: widget.lastUpdated),
+              style: TextStyle(fontSize: 12, color: foreground),
+            ),
+          ],
         ),
-      ],
+      ),
     );
   }
 

lib/state/app/modules/app_modules.dart

@@ -248,6 +248,7 @@ class AppModule {
             mainAxisSize: MainAxisSize.min,
             children: [
               IconButton(
+                tooltip: isVisible ? 'Modul ausblenden' : 'Modul einblenden',
                 onPressed: onVisibleChange,
                 icon: Icon(
                   isVisible