Enhance navigation and error handling; implement global navigator and messenger keys, update schedule progress retrieval, and improve error messaging in various services

bus_terminal/lib/services/exceptions.dart

@@ -1,9 +1,16 @@
 /// Custom exception for authentication errors
+import 'app_navigator.dart';
+
 class UnauthorizedException implements Exception {
   final String message;
-  
-  UnauthorizedException(this.message);
-  
+
+  UnauthorizedException(this.message) {
+    // Trigger centralized logout/navigation asynchronously
+    try {
+      handleAuthExpired(message: message);
+    } catch (_) {}
+  }
+
   @override
   String toString() => message;
 }