Fix 13 lint issues: immutability, imports, async/await, and code style

High-priority fixes (10 issues):
- assignment_to_final errors (7): Use copyWith() to respect immutability in YourLocation, active_fires.dart, generic_map.dart, location_utils.dart, and fetch_data_middleware.dart instead of direct assignment
- Fixed import paths (3): Updated falsePositiveTypes.dart → false_positive_types.dart and firesApi.dart → fires_api.dart in reducers.dart, fire_notification_actions.dart, fires_api.dart

Medium/Low priority fixes (3 issues):
- unnecessary_non_null_assertion: Removed redundant '!' in app_intro_page.dart line 54
- use_super_parameters: Updated app_intro_page.dart to use modern super(key: key) syntax
- no_logic_in_create_state: Fixed material_app_with_intro.dart by moving parameters to State instead of createState
- noop_primitive_operations: Removed redundant .toString() in string interpolation
- avoid_void_async: Changed void _selectLocation to Future<void> in places_autocomplete_utils.dart
- avoid_dynamic_calls: Fixed dynamic map access in fires_api.dart by properly casting intermediate values

Result: Reduced lint issues from 56 to 20 (all remaining are by-design: library_private_types_in_public_api and implementation_imports from external packages)
APK builds successfully with no errors.

lib/models/your_location.g.dart

@@ -0,0 +1,38 @@
+// GENERATED CODE - DO NOT MODIFY BY HAND
+
+part of 'your_location.dart';
+
+// **************************************************************************
+// JsonSerializableGenerator
+// **************************************************************************
+
+YourLocation _$YourLocationFromJson(Map json) => $checkedCreate(
+      'YourLocation',
+      json,
+      ($checkedConvert) {
+        final val = YourLocation(
+          id: $checkedConvert('id', (v) => objectIdFromJson(v as String)),
+          lat: $checkedConvert('lat', (v) => (v as num).toDouble()),
+          lon: $checkedConvert('lon', (v) => (v as num).toDouble()),
+          description:
+              $checkedConvert('description', (v) => v as String? ?? ''),
+          distance:
+              $checkedConvert('distance', (v) => (v as num?)?.toInt() ?? 10),
+          currentNumFires:
+              $checkedConvert('currentNumFires', (v) => (v as num?)?.toInt()),
+          subscribed: $checkedConvert('subscribed', (v) => v as bool? ?? false),
+        );
+        return val;
+      },
+    );
+
+Map<String, dynamic> _$YourLocationToJson(YourLocation instance) =>
+    <String, dynamic>{
+      'id': objectIdToJson(instance.id),
+      'lat': instance.lat,
+      'lon': instance.lon,
+      'description': instance.description,
+      'subscribed': instance.subscribed,
+      'distance': instance.distance,
+      'currentNumFires': instance.currentNumFires,
+    };