feat: harden geofence and distance diagnostics

lib/features/homes/geofence_logic.dart

@@ -0,0 +1,47 @@
+import 'package:geolocator/geolocator.dart';
+
+const double geofenceThresholdMeters = 500.0;
+const Duration geofenceRetryCooldown = Duration(minutes: 30);
+
+bool hasForegroundLocationAccess(LocationPermission permission) {
+  return permission == LocationPermission.whileInUse ||
+      permission == LocationPermission.always;
+}
+
+bool hasBackgroundLocationAccess(LocationPermission permission) {
+  return permission == LocationPermission.always;
+}
+
+Duration? geofenceRetryRemaining(DateTime? lastFailureAt, {DateTime? now}) {
+  if (lastFailureAt == null) return null;
+
+  final currentTime = now ?? DateTime.now();
+  final remaining = lastFailureAt
+      .add(geofenceRetryCooldown)
+      .difference(currentTime);
+  if (remaining <= Duration.zero) {
+    return null;
+  }
+  return remaining;
+}
+
+String formatGeofenceRetry(Duration remaining) {
+  if (remaining.inHours >= 1) {
+    final hours = remaining.inHours;
+    final minutes = remaining.inMinutes.remainder(60);
+    if (minutes == 0) return '$hours ч';
+    return '$hours ч $minutes мин';
+  }
+
+  final minutes = remaining.inMinutes;
+  if (minutes > 0) return '$minutes мин';
+
+  return '${remaining.inSeconds.clamp(1, 59)} сек';
+}
+
+String formatDistanceMeters(double meters) {
+  if (meters < 1000) {
+    return '${meters.round()} м';
+  }
+  return '${(meters / 1000).toStringAsFixed(1)} км';
+}