feat: Add UTM coordinates #38

ref:

test/utils/location_formats_test.dart

@@ -0,0 +1,31 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:meshcore_sar_app/utils/location_formats.dart';
+
+void main() {
+  group('formatUtm', () {
+    test('formats northern hemisphere UTM coordinates', () {
+      expect(formatUtm(37.7749, -122.4194), '10S 551131E 4180999N');
+    });
+
+    test('formats southern hemisphere UTM coordinates', () {
+      expect(formatUtm(-33.8688, 151.2093), '56H 334369E 6250948N');
+    });
+
+    test('falls back to decimal outside the UTM latitude range', () {
+      expect(formatUtm(85, 14.5), '85.00000, 14.50000');
+    });
+  });
+
+  group('formatCoordinates', () {
+    test('formats DMS coordinates', () {
+      expect(
+        formatCoordinates(
+          46.0569,
+          14.5058,
+          CoordinateDisplayFormat.dms,
+        ),
+        '46°03\'24.84"N 14°30\'20.88"E',
+      );
+    });
+  });
+}