feat: Enhance map functionality with download area selection and user location pointer

- Added download area selection feature in MapProvider with methods to enter, exit, and update bounds.
- Implemented DownloadAreaOverlay widget for user interface during download area selection.
- Integrated download area preview in MapManagementScreen with visual feedback.
- Introduced LocationPointer widget to indicate user location and heading on the map.
- Updated localization strings in app_sl.arb for improved clarity and accuracy.
- Refactored map marker generation to utilize the new LocationPointer for user location representation.
- Improved error handling in LocationTrackingService for initial position setting.

lib/providers/map_provider.dart

@@ -1,4 +1,5 @@
 import 'package:flutter/foundation.dart';
+import 'package:flutter_map/flutter_map.dart';
 import 'package:latlong2/latlong.dart';
 import 'package:shared_preferences/shared_preferences.dart';
 import '../models/location_trail.dart';
@@ -27,6 +28,10 @@ class MapProvider with ChangeNotifier {
   // Imported trail (from GPX)
   LocationTrail? _importedTrail;
 
+  // Download area selection
+  bool _isSelectingDownloadArea = false;
+  LatLngBounds? _downloadAreaBounds;
+
   LatLng? get targetLocation => _targetLocation;
   double? get targetZoom => _targetZoom;
   bool get shouldAnimate => _shouldAnimate;
@@ -48,6 +53,10 @@ class MapProvider with ChangeNotifier {
   // Imported trail getters
   LocationTrail? get importedTrail => _importedTrail;
 
+  // Download area getters
+  bool get isSelectingDownloadArea => _isSelectingDownloadArea;
+  LatLngBounds? get downloadAreaBounds => _downloadAreaBounds;
+
   void navigateToLocation({
     required LatLng location,
     double zoom = 15.0,
@@ -302,4 +311,24 @@ class MapProvider with ChangeNotifier {
     _isTrailVisible = true;
     notifyListeners();
   }
+
+  /// Enter download area selection mode with initial bounds
+  void enterDownloadAreaMode(LatLngBounds initialBounds) {
+    _isSelectingDownloadArea = true;
+    _downloadAreaBounds = initialBounds;
+    notifyListeners();
+  }
+
+  /// Exit download area selection mode
+  void exitDownloadAreaMode() {
+    _isSelectingDownloadArea = false;
+    _downloadAreaBounds = null;
+    notifyListeners();
+  }
+
+  /// Update the download area bounds (while dragging/resizing)
+  void updateDownloadAreaBounds(LatLngBounds bounds) {
+    _downloadAreaBounds = bounds;
+    notifyListeners();
+  }
 }