feat: Enhance geofence functionality with new status banners and utility functions

apps/mobile/packages/core/lib/core.dart

@@ -5,6 +5,7 @@ export 'src/core_module.dart';
 export 'src/domain/arguments/usecase_argument.dart';
 export 'src/domain/usecases/usecase.dart';
 export 'src/utils/date_time_utils.dart';
+export 'src/utils/geo_utils.dart';
 export 'src/presentation/widgets/web_mobile_frame.dart';
 export 'src/presentation/mixins/bloc_error_handler.dart';
 export 'src/presentation/observers/core_bloc_observer.dart';

apps/mobile/packages/core/lib/src/utils/geo_utils.dart

@@ -0,0 +1,32 @@
+import 'dart:math';
+
+/// Calculates the distance in meters between two geographic coordinates
+/// using the Haversine formula.
+double calculateDistance(
+  double lat1,
+  double lng1,
+  double lat2,
+  double lng2,
+) {
+  const double earthRadius = 6371000.0;
+  final double dLat = _toRadians(lat2 - lat1);
+  final double dLng = _toRadians(lng2 - lng1);
+  final double a = sin(dLat / 2) * sin(dLat / 2) +
+      cos(_toRadians(lat1)) *
+          cos(_toRadians(lat2)) *
+          sin(dLng / 2) *
+          sin(dLng / 2);
+  final double c = 2 * atan2(sqrt(a), sqrt(1 - a));
+  return earthRadius * c;
+}
+
+/// Formats a distance in meters to a human-readable string.
+String formatDistance(double meters) {
+  if (meters >= 1000) {
+    return '${(meters / 1000).toStringAsFixed(1)} km';
+  }
+  return '${meters.round()} m';
+}
+
+/// Converts degrees to radians.
+double _toRadians(double degrees) => degrees * pi / 180;