feat: harden geofence and distance diagnostics

test/geofence_logic_test.dart

@@ -0,0 +1,41 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:geolocator/geolocator.dart';
+import 'package:ignis_app/features/homes/geofence_logic.dart';
+import 'package:ignis_app/features/homes/providers/location_providers.dart';
+
+void main() {
+  test('distance formatting stays readable across ranges', () {
+    expect(formatDistance(0.42), '420 м');
+    expect(formatDistance(2.34), '2.3 км');
+    expect(formatDistance(12.8), '13 км');
+    expect(formatDistanceMeters(450), '450 м');
+    expect(formatDistanceMeters(1450), '1.4 км');
+  });
+
+  test('distance calculation stays in realistic range', () {
+    final distanceKm = calculateDistanceKm(55.75, 37.61, 55.76, 37.61);
+    expect(distanceKm, closeTo(1.11, 0.15));
+  });
+
+  test('background location access requires always permission', () {
+    expect(hasForegroundLocationAccess(LocationPermission.whileInUse), isTrue);
+    expect(hasBackgroundLocationAccess(LocationPermission.whileInUse), isFalse);
+    expect(hasBackgroundLocationAccess(LocationPermission.always), isTrue);
+  });
+
+  test('retry remaining expires after cooldown window', () {
+    final now = DateTime(2026, 5, 1, 12, 0, 0);
+    final lastFailure = now.subtract(const Duration(minutes: 10));
+    final retryRemaining = geofenceRetryRemaining(lastFailure, now: now);
+
+    expect(retryRemaining, isNotNull);
+    expect(retryRemaining!.inMinutes, 20);
+    expect(
+      geofenceRetryRemaining(
+        now.subtract(const Duration(minutes: 31)),
+        now: now,
+      ),
+      isNull,
+    );
+  });
+}