Update lib/screens/scan_tab.dart

better error message on failed collection loading

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

lib/screens/scan_tab.dart

@@ -43,6 +43,11 @@ class ScanTabState extends State<ScanTab> {
     } catch (e) {
       if (!mounted) return;
       setState(() => _loadingCollections = false);
+      ScaffoldMessenger.of(context).showSnackBar(
+        SnackBar(
+          content: Text('Failed to load collections: $e'),
+        ),
+      );
     }
   }