feat: Add location validation and improve contact latitude/longitude handling

lib/connector/meshcore_connector.dart

@@ -4913,6 +4913,17 @@ class MeshCoreConnector extends ChangeNotifier {
     );
   }
 
+  bool hasValidLocation(double? latitude, double? longitude) {
+    const double epsilon = 1e-6;
+    final lat = latitude ?? 0.0;
+    final lon = longitude ?? 0.0;
+    return (lat.abs() > epsilon || lon.abs() > epsilon) &&
+        lat >= -90.0 &&
+        lat <= 90.0 &&
+        lon >= -180.0 &&
+        lon <= 180.0;
+  }
+
   void _handlePayloadAdvertReceived(
     Uint8List rawPacket,
     Uint8List payload,
@@ -4950,6 +4961,9 @@ class MeshCoreConnector extends ChangeNotifier {
         latitude = advert.readInt32LE() / 1e6;
         longitude = advert.readInt32LE() / 1e6;
       }
+      // Validate location values if present
+      hasLocation = hasValidLocation(latitude, longitude);
+
       if (hasName && advert.remaining > 0) {
         name = advert.readString();
       }
@@ -5015,20 +5029,8 @@ class MeshCoreConnector extends ChangeNotifier {
 
       // CRITICAL: Preserve user's path override when contact is refreshed from device
       _contacts[existingIndex] = existing.copyWith(
-        latitude:
+        latitude: hasLocation ? latitude : existing.latitude,
-            hasLocation &&
+        longitude: hasLocation ? longitude : existing.longitude,
-                latitude != null &&
-                latitude.abs() <= 90 &&
-                (latitude != 0 || longitude != 0)
-            ? latitude
-            : existing.latitude,
-        longitude:
-            hasLocation &&
-                longitude != null &&
-                longitude.abs() <= 180 &&
-                (latitude != 0 || longitude != 0)
-            ? longitude
-            : existing.longitude,
         name: hasName ? name : existing.name,
         path: Uint8List.fromList(path.reversed.toList()),
         pathLength: path.length,

lib/models/contact.dart

@@ -181,12 +181,13 @@ class Contact {
       final lastMod = reader.readUInt32LE();
 
       double? lat, lon;
-      final latRaw = reader.readInt32LE();
+      if (reader.remaining >= 8) {
-      final lonRaw = reader.readInt32LE();
+        final latRaw = reader.readInt32LE();
-
+        final lonRaw = reader.readInt32LE();
-      if (latRaw != 0 || lonRaw != 0) {
+        if (latRaw != 0 || lonRaw != 0) {
-        lat = latRaw / 1e6;
+          lat = latRaw / 1e6;
-        lon = lonRaw / 1e6;
+          lon = lonRaw / 1e6;
+        }
       }
 
       return Contact(