refactored data providers with centralized cache resolution, unified UI using custom dialogs and bottom sheets, and enhanced network error handling for Dio and TLS errors

lib/view/pages/overhang.dart

@@ -42,10 +42,7 @@ class _OverhangState extends State<Overhang> {
             subtitle: const Text('Mit Freunden und deiner Klasse teilen'),
             trailing: const Icon(Icons.arrow_right),
             onTap: () async {
-              final result = await showDialog<ShareTargetType>(
-                context: context,
-                builder: (_) => const SelectShareTypeDialog(),
-              );
+              final result = await showSelectShareTypeSheet(context);
               if (!mounted || result != ShareTargetType.qr) return;
               if (context.mounted) AppRoutes.openQrShare(context);
             },